Status assessment and conservation plan for the western burrowing owl in the United States

              U.S. Fish & Wildlife Service
Status Assessment and
Conservation Plan for the
Western Burrowing Owl
in the United States
Biological Technical Publication
BTP-R6001-2003
© Michael Forsberg
U.S. Fish & Wildlife Service
Status Assessment and
Conservation Plan for the
Western Burrowing Owl
in the United States
Biological Technical Publication
BTP-R6001-2003
David S. Klute1,7
Loren W. Ayers2,8
Michael T. Green3
William H. Howe4
Stephanie L. Jones1
Jill A. Shaffer5
Steven R. Sheffield6,9
Tara S. Zimmerman3
1 U.S. Fish and Wildlife Service, Region 6, Nongame Migratory Bird Program,
Denver, CO
2 Wyoming Cooperative Fish and Wildlife Research Unit, University of Wyoming,
Laramie, WY
3 U.S. Fish and Wildlife Service, Region 1, Nongame Migratory Bird Program,
Portland, OR
4 U.S. Fish and Wildlife Service, Region 2, Nongame Migratory Bird Program,
Albuquerque, NM
5 U.S. Geological Survey, Northern Prairie Wildlife Research Center,
Jamestown, ND
6 U.S. Fish and Wildlife Service, Office of Migratory Bird Management,
Arlington, VA
7 Current Address: Colorado Division of Natural Resources
8 Current Address: Wisconsin Department of Natural Resources
9 Current Address: George Mason University
Author contact information:
David S. Klute, (Current address) Colorado Division
of Wildlife, 6060 Broadway, Denver, CO 80216.
Phone: (303) 291-7320, Fax: (303) 291-7456,
e-mail: David.Klute@state.co.us.
Loren W. Ayers, (Current address) Bureau of
Integrated Science Services, Wisconsin Department
of Natural Resources, 101 S. Webster St., Madison,
WI 53707-7921. Phone: (608) 261-6449, Fax: (608)
266-5226, e-mail: ayersl@mail01.dnr.state.wi.us.
Michael T. Green, U.S. Fish and Wildlife Service,
Region 1, Nongame Migratory Bird Program,
911 Northeast 11th Avenue, Portland, OR 97232.
Phone: (503) 231-6164, Fax: (503) 231-6164,
e-mail: Michael_Green@fws.gov.
William H. Howe, U.S. Fish and Wildlife Service,
Region 2, Nongame Migratory Bird Program,
P.O. Box 1306, Albuquerque, NM 87103.
Phone: (505) 248-6875, Fax: (505) 248-6674,
e-mail: Bill_Howe@fws.gov.
Stephanie L. Jones, U.S. Fish and Wildlife Service,
Region 6, Nongame Migratory Bird Program,
P.O. Box 25486 DFC, Denver, CO 80225-0486.
Phone: (303) 236-4409, Fax: (303) 236-8680,
e-mail: Stephanie_Jones@fws.gov.
Jill A. Shaffer, U.S. Geological Survey, Northern
Prairie Wildlife Research Center, 8711 37th St. SE,
Jamestown, ND 58401. Phone: (701) 253-5547,
Fax: (701) 253-5553, e-mail: jshaffer@usgs.gov.
Steven R. Sheffield, (Current address) Department
of Biology, George Mason University, Fairfax, VA
22030, e-mail: srsheffield@att.net.
Tara S. Zimmerman, U.S. Fish and Wildlife Service,
Region 1, Nongame Migratory Bird Program,
911 Northeast 11th Avenue, Portland, OR 97232.
Phone: (503) 231-6164, Fax: (503) 231-6164,
e-mail: Tara_Zimmerman@fws.gov.
For additional copies or information, contact:
Nongame Migratory Bird Program
U.S. Fish and Wildlife Service
P.O. Box 25486 DFC
Denver, CO 80225-0486
Recommended citation:
Klute, D. S., L. W. Ayers, M. T. Green, W. H. Howe,
S. L. Jones, J. A. Shaffer, S. R. Sheffield, and T. S.
Zimmerman. 2003. Status Assessment and
Conservation Plan for the Western Burrowing Owl
in the United States. U.S. Department of Interior,
Fish and Wildlife Service, Biological Technical
Publication FWS/BTP-R6001-2003, Washington,
D.C.
ii Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
List of Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Taxonomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Legal Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
United States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Canada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Mexico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Distribution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Breeding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Winter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Natural History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Breeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Phenology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Diet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Foraging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Productivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Territory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Aggregations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Mortality and Predation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Site and Burrow Fidelity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Habitat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Breeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Winter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Population Estimates and Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Breeding Bird Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Christmas Bird Count . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Other Surveys, United States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Other Surveys, Canada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Other Surveys, Mexico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Densities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Changes in Breeding Season Distribution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
United States. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Canada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Mexico. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Re-occupancy Rates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
iii
Table of Contents
Monitoring Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Range-wide Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Local Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Proposed Protocols and Surveys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Threats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Habitat: Breeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Habitat Loss and Fragmentation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Burrows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Grazing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Burning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Mowing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Habitat: Winter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Overutilization For Commercial, Recreational, Scientific, or Educational Purposes . . . . . . . . . . . . . . . . . . . . . 22
Predation and Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Predation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Inadequacy of Existing Regulatory Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Other Natural or Manmade Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Disturbance at Nest and Roost Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Ingestion of Plastics, Lead, Etc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Collisions with Stationary/Moving Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Shooting, Trapping, and Hunting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Population Size and Isolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Introduced Species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Indirect Effects of Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Pesticides and Other Contaminants/Toxics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Recommendation on Current Conservation Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Management and Conservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Habitat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Habitat Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Fire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Mowing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Grazing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Burrowing Mammals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Reintroduction and Relocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Reintroduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Relocations and Artificial Burrows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Pesticide Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Monitoring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Wintering Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Education. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Current Activities and Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
United States. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Canada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Research Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
iv Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Appendix A: State Summaries of Burrowing Owl Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Arizona . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
California . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Colorado. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Florida . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Idaho. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Iowa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Kansas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Minnesota . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Montana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Nebraska . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Nevada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
New Mexico. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
North Dakota . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Oklahoma. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Oregon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
South Dakota. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Texas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Utah . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Washington . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Wyoming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Arkansas, Illinois, Missouri, Wisconsin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
Appendix B: Summary of Conservation Recommendations for Burrowing Owls . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Appendix C: Distribution List for the Burrowing Owl Status Assessment and Conservation Plan . . . . . . . . . . . . 94
Appendix D: Scientific and Common Names of Animals and Plants Mentioned
in the Burrowing Owl Status Assessment and Conservation Plan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Table of Contents v
Fig. 1. Current and historical ranges of the Western Burrowing Owl in North America; modified from the
Birds of North America species account (Haug et al. 1993), North American Breeding Bird Survey
distribution map (Sauer et al. 2001), individual papers from the Proceedings of the Second International
Burrowing Owl Symposium (Journal of Raptor Research 35(4) 2001), and personal communications with
local experts. Historical range (pre-1970’s) taken from Zarn (1974), Wedgwood (1978), and from personal
communications with local experts. In states that lacked detailed distributional data, Burrowing Owls were
presumed to be absent from areas of forest or rugged mountains. The historical range is unknown for
Mexico (from Wellicome and Holroyd 2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Fig. 2. Burrowing Owl distribution in Mexico during the breeding (16 April – 15 October) and non-breeding
(16 October – 15 April) seasons as determined from 279 museum specimens and literature documentation
(Enriquez-Rocha 1997). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Fig. 3. Winter distribution of the Burrowing Owls in the United States from Christmas Bird Count (CBC)
data (1966-1989). Shading represents the species relative abundance (birds/100 party hours) averaged for
each CBC circle and smoothed over the species distribution (Sauer et al. 1996). . . . . . . . . . . . . . . . . . . . . . . . . . 11
Fig. 4. Breeding Bird Survey trends for Burrowing Owls in the United States and Canada (1966-96,
Sauer et al. 2002). These trends do not necessarily reflect statistical significance (see Table 2). . . . . . . . . . . . 16
Fig. A-1. Distribution of the Burrowing Owl in Arizona from the Arizona Breeding Bird Atlas project
(Arizona Breeding Bird Atlas, Unpubl. data (1993-2001), C. Wise, pers. commun.) . . . . . . . . . . . . . . . . . . . . . . . 37
Fig. A-2. Distribution of Burrowing Owl Populations in California, 1991-1993 (9,266 breeding pairs,
estimate) (DeSante et al. unpubl. ms.).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Fig. A-3. Distribution of Burrowing Owls in Colorado from the Colorado Breeding Bird Atlas project
(Jones 1998). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Fig. A-4. Distribution of Burrowing Owls in Kansas from the Kansas Breeding Bird Atlas project
(Busby and Zimmerman 2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Fig. A-5. Latilong distribution of Burrowing Owls in Montana. B = direct evidence of breeding,
b = indirect evidence of breeding, t = species observed, but no evidence of breeding (Montana Bird
Distribution Committee 1996). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Fig. A-6. Distribution of Burrowing Owls in Nebraska, based on breeding evidence post-1960
(Ducey 1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Fig. A-7. Distribution of Burrowing Owls in Nevada from the Nevada Breeding Bird Atlas project
(Unpubl. data). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Fig. A-8. Distribution of Burrowing Owls in North Dakota, prior to 1972. Filled squares = nest or
dependent young recorded from 1950 to 1972. Empty squares = nests or dependent young recorded prior
to 1950. Filled triangles = territorial males or pairs recorded from 1950 to 1972. Empty triangles =
territorial males or pairs recorded prior to 1950 (Stewart 1975).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Fig. A-9. Distribution of Burrowing Owls in Oklahoma (Oklahoma Breeding Bird Atlas Project,
D. Reinking, pers. commun.).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Fig. A-10. Distribution of confirmed (n = 49), probable (n = 9), and possible (n = 37) breeding activity
of Burrowing Owls in Oregon from the Oregon Breeding Bird Atlas project (Adamus et al. 2001).. . . . . . . . . 78
vi Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
List of Figures
Fig. A-11. Distribution of Burrowing Owl breeding activity and observation in South Dakota from the
South Dakota Breeding Bird Atlas project (Peterson 1995). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Fig. A-12. Distribution of Burrowing Owl observations in Utah (Utah Natural Heritage Program,
A. Axel, pers. commun.). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Fig. A-13. Distribution of Burrowing Owls burrows in Washington (Washington Department of Fish
and Wildlife, Wildlife Resources Data System, J. Brookshier, pers. commun.).. . . . . . . . . . . . . . . . . . . . . . . . . . 85
Fig. A-14. Historic Burrowing Owl records (dots) from the Wyoming Game and Fish Department
Wildlife Observation System and reoccupancy survey sites with Burrowing Owls (diamonds) in 1999
(from Korfanta et al. 2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Fig. A-15. Numbers of Burrowing Owl records per year in the Wyoming Game and Fish Department
Wildlife Observation System. The trend line for the 1986 – 1997 period represents a period of presumed
consistent search effort (from Korfanta et al. 2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
List of Figures vii
Table 1. Legal status and natural heritage status of Burrowing Owls in the United States, Canada,
and Mexico. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Table 2. North American Breeding Bird Survey trends, significance level (P), sample size (n) and
95% confidence intervals (CI) for the Burrowing Owl during three different survey periods
(Sauer et al. 2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Table 3. Christmas Bird Count trends, sample sizes (n), 95% confidence intervals (CI), significance levels
(P), and relative abundance (RA) for the Burrowing Owl in areas with sufficient data for analysis,
1959-1988 (Sauer et al. 1996). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 4. Burrowing Owl population estimates for states, provinces, and countries. James and Espie
(1997) surveyed state/provincial biologists in 1992 to determine approximate total breeding populations.
Other populations estimates are presented only for statewide/province-wide estimates; additional local
population estimates can be found in Appendix A: State Summaries of Burrowing Owl Status. . . . . . . . . . . . 18
Table A-1. Comparison of mean density, survival, and reproductive rates of Burrowing Owls at four
sites in California.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Table A-2. Estimates of juvenile survival rates necessary for population stability under different
adult reproductive and survival rates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Table A-3. Distribution and abundance of Florida Burrowing Owls by major subpopulation and county. . . . 50
Table A-4. Number of occupied, unoccupied, destroyed, and not found Burrowing Owl nests located in
Washington during Washington Department of Fish and Wildlife surveys in 1999 and 2000. . . . . . . . . . . . . . . 85
Table B-1: General categories of conservation recommendations for Burrowing Owls from states for
which recommendations were found. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
Table D-1: Scientific and common names of animals mentioned in the “Status Assessment and
Conservation Plan for the Western Burrowing Owl in the United States”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Table D-2: Scientific and common names of plants mentioned in the “Status Assessment and
Conservation Plan for the Western Burrowing Owl in the United States”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
viii Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
List of Tables
The Western Burrowing Owl (Athene cunicularia
hypugaea) is a grassland specialist distributed
throughout w. North America, primarily in open
areas with short vegetation and bare ground in
desert, grassland, and shrub-steppe environments.
Burrowing Owls are dependent on the presence
of fossorial mammals (primarily prairie dogs and
ground squirrels), whose burrows are used for
nesting and roosting. Burrowing Owls are protected
by the Migratory Bird Treaty Act in the United
States and Mexico. They are listed as Endangered in
Canada and Threatened in Mexico. They are
considered by the U.S. Fish and Wildlife Service
(USFWS) to be a Bird of Conservation Concern at
the national level, in three USFWS regions, and in
nine Bird Conservation Regions . At the state level,
Burrowing Owls are listed as Endangered in
Minnesota, Threatened in Colorado, and as a Species
of Concern in California, Montana, Oklahoma,
Oregon, Utah, Washington, and Wyoming.
Burrowing Owls historically bred from sc. and sw.
Canada southward through the Great Plains and w.
United States and south to c. Mexico. Although the
historical breeding range is largely intact, range
contractions have occurred primarily at peripheral
regions, in s. Canada, the ne. Great Plains, and parts
of California and the Pacific Northwest. Burrowing
Owls winter in the sw. and sc. United States,
throughout Mexico, and occasionally as far south
as Panama.
Populations of Burrowing Owls have declined in
several large regions, notably in the ne. Great Plains
and Canada. However, estimates of population
trends in many regions are generally inconclusive
due to small samples sizes and high data variability.
Population trends as determined from North
American Breeding Bird Survey (BBS) data were
inconsistent, with some regions exhibiting positive
trends and other regions exhibiting negative trends.
When taken as a whole, the BBS indicated an area
of generally declining populations in the northern
half of the Great Plains, and generally increasing
populations in the interior U.S. and in some
southwestern deserts. The Christmas Bird Count
indicated a significant population decline in
California (1966-1989). Local surveys have detected
declining populations and/or range reductions in
California, Iowa, Kansas, Minnesota, Nebraska,
New Mexico, North Dakota, Oklahoma, Oregon,
South Dakota, Texas, Washington, and throughout
the range of the species in Canada.
Primary threats across the North American range
of the Burrowing Owl are habitat loss due to land
conversions for agricultural and urban development,
and habitat degradation and loss due to reductions
of burrowing mammal populations. The elimination
of burrowing mammals through control programs
and habitat loss has been identified as the primary
factor responsible for declines of Burrowing Owls.
Additional threats to Burrowing Owls include
habitat fragmentation, predation, illegal shooting,
pesticides and other contaminants. The types and
significance of threats during migration and
wintering are poorly understood.
The preservation of native grasslands and
populations of burrowing mammals is ultimately
critical for the conservation of Burrowing Owls.
Efforts to maintain and increase populations of
burrowing mammals through reduction of lethal
control programs and landowner and land manager
education should be undertaken. Burning, mowing,
and grazing may be employed to maintain suitable
habitat structure for nesting Burrowing Owls,
although additional research is needed. Efforts to
reintroduce or relocate Burrowing Owls should be
critically reviewed to determine efficacy and best
methods. Current large-scale monitoring efforts
are generally inadequate. Effective programs to
better determine actual population trends and
demographics of Burrowing Owl populations should
be developed and implemented.
1
Executive Summary
Many individuals contributed significant time,
literature, and expertise to this review including: R.
Anthony, A. Axel, P. Arrowood, E. Atkinson, A.
Bammann, J. Barclay, J. Belthoff, J. Brookshier, N.
Brown, K. Brunson, D. Buckland, K. Burton, W.
Busby, K. Butts, K. Clayton, L. Cole, C. Collins, C.
Conway, T. Corman, E. Cummings, C. Cwiklinski, N.
Dawson, K. De Smet, M. Desmond, J. Dinsmore, B.
Domagalski, E. Dowd-Stukel, F. Esparza, C. Finley,
T. Floyd, L. Fredrickson, D. Freed, J. Freilich, J.
Friday, S. Grassel, R. Griebel, D. Harvey, M.
Hetrick, B. Hodorff, G. Holroyd, S. Houston, M.
Howery, S. Hutchings, L. Igl, D. Keinath, S. Kendall,
N. Korfanta, J. Lincer, M. Lockwood, M. Martell, D.
Mehlman, B. Millsap, P. Mineau, S. Moore, R.
Murphy, J. Parrish, R. Peterson, D. Plumpton, D.
Reinking, T. Rich, D. Rintoul, L. Romin, M. Rowe, C.
Rustay, L. Sager, K. Scalise, J. Schmutz, C.
Shackelford, G. Skiba, M.K. Skoruppa, J. Slater, K.
Steenhof, C. Stowers, L. Trulio, T. Uhmann, T.
VerCauteren, B. Vermillion, T. Wellicome, R.
Williams, J. Winter, C. Wise, M. Woodin, J. Woollett,
and J. Yamamoto.
Special thanks to G. Holroyd and T. Wellicome, with
the Canadian Wildlife Service, for assistance in
gathering literature, providing maps and graphs,
and making contacts. Special thanks also to D.
Rosenberg for providing additional information and
thorough reviews. T. Uhmann and N. Brown
provided bibliographies. M. J. Cowing and the
Richard R. Olendorff Memorial Library at the
Forest and Rangeland Ecosystem Science Center
provided extensive literature. P. Sutherland provided
assistance compiling the literature and editing the
manuscript. Thanks also to D. Dark, K. Sims, and L.
Semo for assistance with literature review,
compiling, and editing. Thanks to A. Araya for
providing valuable assistance.
We thank the following for providing reviews of
an earlier draft: J. Barclay, B. Busby, J. Dillon, C.
Finley, K. M. Giesen, D. B. Hall, L. Hanebury, G.
Holroyd, N. Korfanta, D. W. Mehlman, E. J. Miller,
R. K. Murphy, D. Rosenberg, J. S. Shackford, S.
Sherrod, K. Steenhof, T. VerCauteren, and R. D.
Williams.
2 Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Acknowledgments
Two subspecies of Burrowing Owl (Athene
cunicularia) occur in North America: the Western
Burrowing Owl (A. c. hypugaea) and the Florida
Burrowing Owl (A. c. floridana). Although this
status assessment is focused on North American
populations of the Western Burrowing Owl
(henceforth Burrowing Owl), a state summary for
the Florida Burrowing Owl is included in this
document (Appendix A) to provide complete
information on the species in the United States. The
Florida state summary is an update of information
included in Millsap (1996).
Class: Aves
Order: Strigiformes
Family: Strigidae
Genus: Athene
Species: A. cunicularia
Subspecies: A. c. hypugaea, A. c. floridana
Authority: (Molina, Subspp. Bonaparte)
Originally named Strix cunicularia by Molina in
1782, the Burrowing Owl received several taxonomic
changes until placed in the genus Speotyto and now
Athene (Clark et al. 1997, AOU 1998). A. cunicularia
occurs as a breeding and/or wintering species
throughout w. North America, Central America, and
extensive portions of South America with disjunct
populations in Florida and the Caribbean Islands. A.
c. hypugaea occurs in North America to the eastern
limits of the Great Plains and from s. British
Columbia to Manitoba and into Central America as
far south as Panama (Haug et al. 1993). This
subspecies occurs primarily in prairies, grasslands,
shrub-steppe, desert, and agricultural areas in
North America (Haug et al. 1993). A. c. floridana
occurs in Florida north to Madison and Duval
counties (AOU 1998).
3
Taxonomy
United States
From 1994-1996, the Western Burrowing Owl was
designated by the U.S. Fish and Wildlife Service
(USFWS) as a Category 2 species for consideration
to be listed as a threatened or endangered species.
In 1996 the Category 2 designation was
discontinued. The Burrowing Owl currently is
federally protected by the Migratory Bird Treaty
Act (1918) in the United States and Mexico. The
Western Burrowing Owl is listed by the USFWS as a
National Bird of Conservation Concern (U.S. Fish
and Wildlife Service 2002). It is also listed as a Bird
of Conservation Concern in USFWS Regions 1
(Pacific Region, mainland only), 2 (Southwest
Region), and 6 (Mountain-Prairie Region) as well as
in Bird Conservation Regions (BCR) 9 (Great
Basin), 11 (Prairie Potholes), 16 (S. Rockies/Colorado
Plateau), 17 (Badlands and Prairies), 18 (Shortgrass
Prairie), and U.S. Portions of BCR 32 (Coastal
California), 33 (Sonoran and Mojave Deserts), 35
(Chihuahuan Desert) and 36 (Tamaulipan
Brushlands) (U.S. Fish and Wildlife Service 2002).
The Burrowing Owl is listed as Endangered,
Threatened, or as a Species of Concern in 9 states
and 4 Canadian provinces (Table 1). It is given a
Global Heritage Status Rank of G4 (apparently
secure globally though it may be quite rare in parts
of its range) and is listed as a Convention on
International Trade in Endangered Species
(CITES), Appendix II species (NatureServe
Explorer 2001).
Canada
In 1979, the Western Burrowing Owl was listed as
“Threatened” based on Wedgwood (1979),
reconfirmed in 1991 (Haug and Didiuk 1991), and
changed to “Endangered” in 1995 (Wellicome and
Haug 1995).
Mexico
In 1994, Burrowing Owls were listed as a federally
Threatened (Amenazadas) species (Secretaria de
Desarollo Social de Mexico 1994 in Sheffield 1997a).
4 Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Legal Status
Legal Status 5
Table 1. Legal status and natural heritage status of Burrowing Owls in the United States, Canada, and Mexico
Area Legal status Natural Heritage statusa
United States None Apparently Secure
Arizona None Vulnerable
California Species of Concern Imperiled
Colorado Threatened Apparently Secure
Idaho None Vulnerable/Apparently Secure
Iowa Accidental breeder Unranked
Kansas None Vulnerable
Minnesota Endangered Critically Imperiled
Montana Species of Concern Vulnerable
Nebraska None Vulnerable
Nevada None Vulnerable
New Mexico None Apparently Secure
North Dakota None Unranked
Oklahoma Species of Concern Vulnerable
Oregon Species of Concern Imperiled
South Dakota None Vulnerable/Apparently Secure
Texas None Vulnerable
Utah Species of Concern Vulnerable
Washington Species of Concern Vulnerable
Wyoming Species of Concern Vulnerable
Canada Endangered Vulnerable
Alberta Endangered Vulnerable
British Columbia Endangered Critically Imperiled
Manitoba Endangered Critically Imperiled
Saskatchewan Endangered Imperiled
Mexico Threatened Unranked
a–Global status = Apparently Secure
The Burrowing Owl is a small owl (19.5-25.0 cm,
~150 g), with long slender tarsi covered with short
hair-like feathers that terminate in sparse bristles
on the feet. The head is rounded, lacks ear tufts, and
is chocolate in color with white streaking or spotting.
There are buffy-white margins around the eyes and
a white throat patch. Eyes are lemon-yellow and the
beak is pale horn-colored. The wings are relatively
long and rounded, the tail is short, and both are
brown with buff-white barring. The undertail
coverts are white. The dorsal area including head,
back, and scapulars are heavily spotted with buffy-white.
The belly of adults is buffy and heavily barred
with brown on the sides. Juveniles are similar to
adults but are unstreaked to lightly streaked, light
to brownish buff below, and have more pale
secondary coverts (Haug et al. 1993). The Burrowing
Owl is the only North American strigiform not
exhibiting reversed size dimorphism (Haug et al.
1993).
6 Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Description
Breeding
In Canada, the historical breeding range of the
Burrowing Owl includes se. British Columbia, s.
Alberta, s. Saskatchewan, and sw. Manitoba (Fig. 1,
Haug et al. 1993, Wellicome and Holroyd 2001). In
the United States the historical breeding range
includes e. Washington and Oregon, s., c. and e.
California, c. and e. Montana, s. Idaho, Utah,
Nevada, Arizona, Wyoming, Colorado, New Mexico,
North Dakota, South Dakota, Nebraska, w. and c.
Kansas, w. and c. Oklahoma, w. Minnesota, nw. Iowa,
and most of w. Texas (Fig. 1). The breeding range
has contracted primarily on the eastern and
northern edges (Wellicome and Holroyd 2001).
Anecdotal observations suggest accidental breeding
may have occurred in Wisconsin (R. Domalgalski,
pers. commun.). Migrants or vagrants have been
documented in Louisiana (B. Vermillion, pers.
commun.), Missouri (Haug et al. 1993), Arkansas
(James and Neal 1986), and Illinois (Illinois Natural
History Information Network 2000). The breeding
range extends south to c. Mexico (Fig. 1, Fig. 2)
(Enriquez-Rocha 1997, Wellicome and Holroyd 2001).
Migration
Little information exists on migration routes and
times. Burrowing Owls migrate north during March
and April, arriving the first week of May in
Saskatchewan (Haug et al. 1993). The majority of
Burrowing Owls that breed in Canada and the n.
United States are believed to migrate south during
September and October.
Burrowing Owls banded in British Columbia,
Washington, Oregon, and California migrated
southward along the Pacific coast. Burrowing Owls
banded in Alberta, Saskatchewan, Manitoba,
Montana, and North Dakota migrated southward
through Nebraska and Kansas into Texas. One
Burrowing Owl from Manitoba was recovered in the
Gulf of Mexico. Burrowing Owls banded in
Wyoming, South Dakota, Nebraska, Colorado,
Kansas, and Oklahoma have been recovered in
Arkansas, Oklahoma, Texas, and Mexico. Recoveries
indicate that some Burrowing Owls will winter in
California and Baja California, Mexico. Burrowing
Owls breeding in North and South Dakota are
believed to winter in Texas.
Winter
The small number of banding recoveries (n = 27,
1927 through 1990) provides little information
regarding wintering areas (Haug et al. 1993).
Burrowing Owls winter regularly from Mexico (Fig.
2) to El Salvador and are casual to accidental to w.
Panama (AOU 1998). They are recorded on the
Christmas Bird Count (CBC) in Arizona, California,
New Mexico, Oregon, Texas, and Mexico (Fig. 3;
James and Ethier 1989). They will also winter north
of these states, particularly in Oklahoma and
Kansas, in very low abundance. They will also winter
in low abundance in sc. Nevada (Hall et al. In
review).
Little information exists on Burrowing Owls in
Mexico and breeding and wintering areas have not
been well described. Based on museum specimens,
the Burrowing Owl is the third most common owl
species in the country and sixty-three percent of
museum specimens (n = 279) from Mexico were
collected in the non-breeding season (Enriquez-
Rocha 1997); however, it is unlikely that these
collections reflect true relative abundance. These
collections documented a wide distribution,
occurring in 28 of the 32 Mexican states. Non-breeding
data were from the Pacific region, some
central states, and from the se. Gulf of Mexico
(including the Yucatan Peninsula). Both breeding
and nonbreeding records document Burrowing Owls
in n. Mexico, Baja California, and some states from
the Gulf of Mexico.
7
Distribution
8 Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Fig. 1. Current and historical ranges of the Western Burrowing Owl in North America; modified from the
Birds of North America species account (Haug et al. 1993), North American Breeding Bird Survey
distribution map (Sauer et al. 2001), individual papers from the Proceedings of the Second International
Burrowing Owl Symposium (Journal of Raptor Research 35(4) 2001), and personal communications with
local experts. Historical range (pre-1970’s) taken from Zarn (1974), Wedgwood (1978), and from personal
communications with local experts. In states that lacked detailed distributional data, Burrowing Owls were
presumed to be absent from areas of forest or rugged mountains. The historical range is unknown for
Mexico (from Wellicome and Holroyd 2001).
Manitoba
Saskatchewan
Alberta
British Columbia
Washington
Oregon
Nevada
Idaho
Montana
North Dakota
South Dakota
Nebraska
Kansas
Oklahoma
Texas
Coahuila
Zacatecas
Utah Colorado
Arizona New Mexico
Sonora
California
Baja
California
Norte
Baja
California
Sur
Iowa
Minnesota
Wyoming
Nuevo
Leon
Chihuahua
Durango
San Luis
Current breeding range (1990s) Potosi
Historical breeding range
Distribution 9
Fig. 2. Burrowing Owl distribution in Mexico during the breeding (16 April – 15 October) and non-breeding
(16 October – 15 April) seasons as determined from 279 museum specimens and literature documentation
(Enriquez-Rocha 1997).
Breeding Season
Nonbreeding Season
Both Seasons
No Records
Gulf of Mexico
Pacific Ocean
N
Breeding
Phenology—Burrowing Owls are generally found on
the northern breeding grounds from mid-March
through September (Haug et al. 1993). Courtship
and pair formation occur in March and April in most
areas (Grant 1965, Butts 1973) but may begin as
early as late December in California (Thomsen 1971).
Incubation lasts 28-30 days and is performed by the
female (Coulombe 1971, Thomsen 1971, Haug et al.
1993). The young begin feathering out at two weeks
of age. The young run and forage by four weeks of
age and are capable of sustained flight by six weeks.
Burrowing Owl families often switch burrows every
10-15 days when the young are three to four weeks
old and remain as a loose-knit group until early fall
when the young may begin to disperse to nearby
burrows (Haug et al. 1993, Dechant et al. 1999).
Diet—Burrowing Owls are opportunistic feeders,
primarily taking arthropods, small mammals, birds,
amphibians and reptiles (Haug et al. 1993). Seasonal
variability in food habits occurs, with vertebrates
occurring more commonly in the winter diet and
arthropods occurring more frequently in the
summer diet (Haug et al. 1993).
Foraging—Burrowing Owls forage in a variety of
habitats, including cropland, pasture, prairie dog
colonies, fallow fields, and sparsely vegetated areas
(Butts and Lewis 1982, Thompson and Anderson
1988, Desmond 1991, Haug et al. 1993, Wellicome
1994). Vegetation >1 m tall may be too tall for
Burrowing Owls to locate or catch prey (Haug and
Oliphant 1987, 1990; Wellicome 1994).
Productivity—Burrowing Owls are capable of
breeding at one year of age. However, some females
may not breed the first year after hatching, or may
breed away from the natal site the first year after
hatching and then return to the natal site in their
second year after hatching (Lutz and Plumpton
1999). Second broods have rarely been documented
in the Burrowing Owl (Haug et al. 1993). Average
clutch size over the range of the species was 6.5 eggs
(range 4-12; Haug et al. 1993). In Canada, percent
successful reproduction ranged from 45-97% and
mean fledging rate ranged from 2.1 to 6.3 young/
successful nest (Hjertaas et al. 1995). In British
Columbia, 58% (n = 12) of nesting attempts were
successful and produced 31 young with a mean brood
size of 4.1±1.3 young/successful nest and 2.6 young/
attempt (Hjertaas et al. 1995). In Manitoba, average
brood size was 5.1 young and overall productivity
was 3.4 young/nesting pair (De Smet 1997). In New
Mexico, Burrowing Owls produced 3.33 ± 1.49
nestlings and 2.55 ± 1.49 fledglings in human-altered
habitats and 1.05 ± 1.23 nestlings and 0.68 ± 0.98
fledglings in natural habitats (Botelho and Arrowood
1996).
Territory—Burrowing Owls generally stay close to
the nest burrow during daylight and forage farther
from the nest between dusk and dawn (Haug 1985,
Haug and Oliphant 1990). Nesting-territory size was
4.8-6.4 ha in Minnesota (n = 2) and 4-6 ha in North
Dakota (n = estimated 5-9 pairs) (Grant 1965).
Average diurnal ranges of Burrowing Owls in e.
Wyoming encompassed 3.5 ha (number of foraging
areas not given) (Thompson 1984). Foraging-areas
are considerably larger than nesting-areas. In s.
Saskatchewan, mean foraging territory size for
males ranged from 14 to 481 ha (mean = 241 ha; n =
6) (Haug 1985, Haug and Oliphant 1990). In a heavily
cultivated region of s. Saskatchewan, foraging
territories for males averaged 35 ha (n = 4) (Sissons
et al. 2001).
Aggregations—In nc. Colorado, mean inter-nest
distances for Burrowing Owls nesting in black-tailed
prairie dog colonies was 101 m (n = 8) (Plumpton
1992). Mean nearest-neighbor distance for
Burrowing Owls nesting in 20 American badger
excavations in w. Nebraska was 240 m, compared to
mean nearest-neighbor distances of 105 m for 118
non-clustered nests in small prairie dog colonies and
125 m for 105 nest clusters in large prairie dog
colonies (Desmond 1991, Desmond et al. 1995,
Desmond and Savidge 1996). Available excavations
may be limiting to Burrowing Owls nesting outside
of prairie dog colonies
Within prairie dog colonies, Burrowing Owls have
been observed to aggregate their nests into clusters.
Mean densities of Burrowing Owls within clusters in
larger colonies (≥ 35 ha) were 1.2-1.3 individuals/ha
(n = 21). In smaller colonies (<35 ha) with random
distributions, mean densities of Burrowing Owls
ranged from 1.7 to 5.8 individuals/ha (n = 26).
Clustered nest distributions may reduce depredation
risks by allowing individuals to alert one another to
potential predators (Butts 1973, Desmond 1991,
Desmond et al. 1995, Desmond and Savidge 1996).
10 Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Natural History
In ne. Colorado, 27 prairie dog colonies with
Burrowing Owls ranged in size from 1.9 to 167.6 ha
(Hughes 1993). In w. Nebraska, fledging success
rates were positively correlated with the size of
prairie dog colonies (Desmond 1991).
Mortality and Predation—The annual mortality
rate in Oklahoma was estimated at 62% (adults and
young combined) (Butts 1973). At two sites in s.
Saskatchewan, adult female survival (s) (s = 0.62, n
=12 and s = 1.00, n = 2) was higher than survival
for adult males (s = 0.48, n = 11 and s = 0.38, n = 5)
or juveniles (s = 0.45, n = 21 and s = 0.48, n = 25)
(Clayton and Schmutz 1999).
Predators of Burrowing Owls include badger,
domestic cat, weasel, skunk, domestic dog, coyote,
Swainson’s, Ferruginous, Red-tailed, and Cooper’s
hawks, Merlin, Prairie, and Peregrine falcons, Great
Horned Owl, American Crow (Haug et al. 1993),
snakes, bobcats and Northern Harrier (Leupin and
Low 2001).
Site and Burrow Fidelity—Individual Burrowing
Owls have moderate to high site fidelity to general
breeding areas, prairie dog colonies, and even to
particular nest burrows. Of 31 adults banded in
Colorado in 1990, 39% returned in 1991, whereas only
5% of 369 Burrowing Owls banded as nestlings prior
to 1994 returned in one or more years after hatch
(Plumpton and Lutz 1993, Lutz and Plumpton 1999).
Eight of the remaining 12 returning adults (66%)
reused the same prairie dog town as the prior year
(Plumpton and Lutz 1993). Adult males and females
returned at similar rates (19% and 14%, respectively)
(Lutz and Plumpton 1999). Adult males and females
nested in formerly used sites at similar rates (75%
and 63%, respectively). In Albuquerque, New
Mexico, all returning males selected the same
burrow they had previously inhabited unless the
burrow had been destroyed (n = 9, Martin 1973). In
Manitoba, 7% of failed nests (n = 57) were reused in
consecutive years but 23% (n = 122) of successful
nests were reused (De Smet 1997). Burrow fidelity
has been reported in some areas; however, more
frequently, Burrowing Owls reuse traditional
nesting areas without necessarily using the same
burrow (Haug et al. 1993, Dechant et al. 1999).
Burrow and nest sites are re-used at a higher rate if
the bird has reproduced successfully during the
previous year (Haug et al. 1993).
Natural History 11
Fig. 3. Winter distribution of Burrowing Owls in the United States from Christmas Bird Count (CBC) data
(1966-1989). Shading represents the species relative abundance (birds/100 party hours) averaged for each
CBC circle and smoothed over the species distribution (Sauer et al. 1996).
Breeding
Burrowing Owl nesting habitat consists of open
areas with mammal burrows. They use a wide
variety of arid and semi-arid environments, with
well-drained, level to gently sloping areas
characterized by sparse vegetation and bare ground
(Haug et al. 1993, Dechant et al. 1999). Breeding
habitats include native prairie, tame pasture,
hayland, fallow fields, road and railway rights-of-way,
and urban habitats (e.g., campuses, airports,
and golf courses) (Dechant et al. 1999). Burrowing
Owls do not occupy all apparently available habitat
(i.e., prairie dog or ground squirrel colonies).
Unused colonies have been documented in
virtually all states within the current range
of the Burrowing Owl.
Burrowing Owls require a mammal burrow or
natural cavity surrounded by sparse vegetation.
Burrow availability is often limiting in areas lacking
colonial burrowing rodents (Desmond and Savidge
1996). Burrowing Owls frequently use burrows of
black-tailed prairie dogs. They nest less commonly
in the burrows of Douglas’ ground squirrels, white-tailed
prairie dogs, Gunnison’s prairie dogs, yellow-bellied
marmots, woodchucks, skunks, foxes,
coyotes, and nine-banded armadillos (Dechant et al.
1999). Where mammal burrows are scarce,
Burrowing Owls have been found nesting in natural
rock and lava cavities (Gleason 1978, Gleason and
Johnson 1985, Rich 1986).
Burrowing Owls may use “satellite” or non-nesting
burrows, moving chicks at 10-14 days presumably to
reduce risk of predation (Desmond and Savidge
1998) and possibly to avoid nest parasites (Dechant
et al. 1999). Successful nests in Nebraska had more
active burrows within 75 m of the nest burrow than
unsuccessful nests (Desmond and Savidge 1999).
Observations made at 15 burrow sites by James and
Seabloom (1968) revealed that family units in sw.
North Dakota used from one to three satellite
burrows, although a few family units used from two
to ten satellite burrows. In e. Wyoming, most (actual
number not given) nesting areas contained between
two and 11 available burrows (Thompson 1984).
Three Burrowing Owl families in Iowa used from
one to five satellite burrows (Scott 1940). In
Oklahoma, black-tailed prairie dog colonies
appeared to be the only habitat with a sufficient
density of burrows to provide satellite burrows for
Burrowing Owls (Butts and Lewis 1982).
Migration
No information is available on migration habitats.
They are presumed to be similar to breeding
habitats (Haug et al. 1993).
Winter
Little is known about wintering habitat
requirements beyond what the species uses during
the breeding season, but there seems to be increased
use of agricultural fields with culverts in some areas
(Haug et al. 1993, W. Howe, pers. commun.). In
Louisiana, in winter, Burrowing Owls are typically
found in dune vegetation or near woody debris on
beaches, in pastures, and in agricultural fields (B.
Vermillion, pers. commun.). In sc. Nevada, burrows
used in winter were the same as those used during
the breeding season (Hall et al. In review).
12 Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Habitat
Population Estimates and Trends
Breeding Bird Survey—The Breeding Bird Survey
(BBS) revealed a mixture of population trends
throughout the Burrowing Owl breeding range in
North America (Table 2, Fig. 4) (Sauer et al. 2002).
BBS trends for Burrowing Owls are largely limited
by small sample sizes and the species is not
adequately sampled over a large part of their
breeding range. Trends in nearly all regions are
limited by important or potential deficiencies (Sauer
et al. 2002). However, when taken as a whole,
generally declining populations are present in the
northern half of the Great Plains, and generally
increasing populations are present in the northwest
interior and in some southwestern deserts of the
United States (Table 2, Fig. 4).
Christmas Bird Count—Burrowing Owl abundance
is poorly monitored by the CBC. Most Burrowing
Owls from the Great Plains winter in Mexico where
CBC coverage is poor. On the Gulf Coast of Texas,
wintering Burrowing Owls are difficult to detect and
samples sizes are small. The effort to locate
wintering Burrowing Owls has increased in recent
years (G. Holroyd, pers. commun.). A significant
decreasing trend was observed only in California;
trends for other areas were non-significant (Table 3)
(Sauer et al. 1996). James and Ethier (1989) detected
stable populations in most wintering areas in New
Mexico, Louisiana, and Mexico for 1955-85. There
were no significant changes in Arizona, New Mexico,
Texas, and Louisiana from 1954-86, or in Mexico
between 1974 and 1985 (James and Ethier 1989)
Other Surveys, United States—Surveys in
California in 1986-91 found population decreases of
23-52% in the number of breeding groups and 12-
27% in the number of breeding pairs of owls
(DeSante et al. 1997). Populations in w. Nebraska
declined 58% (91 to 38 nesting pairs) between 1990-
1996 (Desmond and Savidge 1998). Populations in
New Mexico have exhibited mixed trends: stable or
increasing populations were associated with the
presence of suitable habitat and increased
precipitation and food availability while decreasing
populations were associated with loss of suitable
habitat (Arrowood et al. 2001). In Wyoming, only 11%
of 86 historical sites were occupied in 1998; however,
the importance of this finding is uncertain due to the
tendency for Burrowing Owl colonies to move
(Korfanta et al. 2001). The Wyoming Game and Fish
Department’s Wildlife Observation System showed
populations generally increasing between 1974-80
and then decreasing between 1981-97 (Korfanta et al.
2001). In North Dakota, Burrowing Owls have
disappeared from the eastern third of the state and
is uncommon to rare in the best habitats north and
east of the Missouri River (Murphy et al. 2001). In
sw. North Dakota the current population trend is not
clear, but is probably closely tied to populations of
prairie dogs (Murphy et al. 2001). Based on
questionnaires, literature searches, personal
contacts and field observations, Brown (2001)
concluded that Burrowing Owls are widespread but
uncommon in Arizona. In Oklahoma there are an
estimated 800-1000 breeding Burrowing Owls,
restricted primarily to the panhandle of the state
(Sheffield and Howery 2001). In a survey of National
Grasslands, Sidle et al. (2001) found higher
occupancy of active prairie dog towns in the
southern Great Plains (93%) than in the northern
Great Plains (59%).
13
Populations
Table 2. North American Breeding Bird Survey trends, significance level (P), sample size (n) and 95% confidence intervals (CI) for the Burrowing Owl during three
different survey periods (Sauer et al. 2002).
1966–2001 1966–1979 1980–2001
Area (data credibility)a Trendb P n 95% CI Trendb P n Trendb P n
State/Province
Alberta (R) –8.5 0.42 6 –27.2 10.1 51.8 0.26 3 3.9 0.93 3
Arizona (Y) 7.7 0.65 9 –23.8 39.20 — — — –3.1 0.88 8
California (B) 5.9 0.01 32 1.9 9.8 –0.9 0.92 19 5.4 0.03 24
Colorado (Y) –4.0 0.48 38 –14.9 6.9 –7.8 0.40 9 2.7 0.57 36
Idaho (R) 19.1 0.07 9 1.4 36.8 39.2 0.03 3 28.4 0.06 9
Kansas (Y) –1.1 0.80 11 –9.1 7.0 10.8 0.34 8 11.7 0.69 8
Montana (R) –12.6 0.11 10 –26.5 1.3 — — — –14.8 0.19 9
Nebraska (Y) 6.5 0.57 13 –14.9 27.9 33.9 0.11 8 3.8 0.72 8
Nevada (Y) 10.9 0.30 9 –8.2 30.1 0.9 0.97 3 12.1 0.14 6
New Mexico (Y) 0.7 0.85 37 –7.0 8.4 -3.9 0.03 6 2.2 0.77 35
North Dakota (R) –3.2 0.44 13 –10.9 4.6 19.6 0.15 7 -15.8 0.00 9
Oklahoma (R) -11.5 0.00 10 -14.1 –8.8 14.2 0.37 6 –4.5 0.34 8
Oregon (Y) 3.8 0.63 11 –11.0 18.5 –14.2 0.66 5 15.5 0.20 8
Saskatchewan (R) -26.0 0.04 2 -29.3 –22.7 — — �� — — —
South Dakota (Y) –7.2 0.16 19 –16.9 2.5 5.2 0.52 14 -11.4 0.08 10
Texas (Y) –1.9 0.39 28 –6.3 2.4 8.4 0.27 14 –5.2 0.26 24
Utah (Y) 0.9 0.89 14 –11.3 13.0 — — — –6.6 0.14 14
Washington (Y) –7.8 0.60 7 –35.2 19.7 — — — –19.4 0.20 6
Wyoming (Y) -23.7 0.04 11 -42.3 –5.2 10.5 0.76 2 5.9 0.53 9
Physiographic strata
South Texas Brushlands –3.9 0.46 2 –10.9 3.0 — — — — — —
High Plains Border (Y) 5.7 0.45 17 –8.5 19.8 3.1 0.84 11 20.0 0.55 11
High Plains (Y) –4.0 0.43 50 –14.0 6.0 –1.9 0.85 17 2.4 0.61 46
Drift Prairie (Y) -26.0 0.01 8 -37.7 –14.3 –13.5 0.40 7 — — —
14 Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Table 2. Continued
1966–2001 1966–1979 1980–2001
Area (data credibility)a Trendb P n 95% CI Trendb P n Trendb P n
Glaciated Missouri Plateau (R) -11.0 0.04 15 -20.0 –2.0 23.0 0.12 6 –12.8 0.16 10
Great Plain Roughlands (R) –2.6 0.40 30 –8.6 3.4 16.9 0.03 12 –10.4 0.04 22
Rolling Red Plains (Y) –0.9 0.77 7 –7.0 5.1 –2.7 0.81 3 1.1 0.75 7
Staked Plains (B) –2.3 0.39 21 –7.6 2.9 10.3 0.27 10 –4.3 0.38 19
Chihuahuan Desert (Y) 1.8 0.80 22 –12.2 15.8 43.4 0.33 7 –1.1 0.90 20
Great Basin Deserts (Y) 7.3 0.55 8 –15.3 29.9 — — — –1.9 0.83 8
Mexican Highlands (Y) 7.1 0.42 2 –3.6 17.8 — — — –8.1 0.55 2
Sonoran Desert (Y) 6.6 0.03 10 1.6 11.5 –2.6 0.84 5 5.7 0.11 8
Mojave Desert (Y) –1.4 0.84 6 –14.4 11.6 20.6 0.36 4 –20.2 0.33 4
Wyoming Basin (Y) -31.0 0.07 4 -53.6 –8.4 10.5 0.76 2 29.0 0.60 2
Intermountain Grassland (Y) 2.8 0.57 27 –6.7 12.3 — — — 6.8 0.03 23
Basin and Range (Y) 9.9 0.30 13 –7.8 27.6 0.7 0.96 3 5.8 0.43 10
Columbia Plateau (R) 12.8 0.04 28 1.1 24.4 33.0 0.00 9 21.6 0.01 24
Central Valley (Y) 2.6 0.41 15 –3.3 8.5 –9.6 0.65 9 1.4 0.76 12
USFWS Regions
Region 1 (Y) 7.1 0.00 68 3.5 10.7 5.7 0.41 31 7.2 0.00 53
Region 2 (Y) –1.2 0.45 84 –4.4 2.0 –0.5 0.72 29 –1.8 0.63 75
Region 6 (Y) –4.4 0.29 129 –12.6 3.7 –0.7 0.92 48 –0.2 0.95 103
Country
Canada (R) -12.1 0.01 8 -18.4 –5.9 23.8 0.36 4 -18.7 0.02 4
United States (Y) –1.5 0.57 291 –6.5 3.6 0.0 0.99 113 1.6 0.40 237
Survey-wide (Y) -1.5 0.57 299 –6.5 3.6 0.2 0.96 117 1.5 0.41 241
a–Data credibility measure. (R) = RED: Data with an important deficiency. (Y) = Yellow: Data with a potential deficiency. (B) = BLUE: Data with at least 14 samples in the long term, of moderate precision,
and of moderate abundance on routes.
b–Mean percent change per year
Populations 15
Fig. 4. Breeding Bird Survey trends for Burrowing Owls in the United States and Canada (1966-96, Sauer et
al. 2002). These trends do not necessarily reflect statistical significance (see Table 2).
Table 3. Christmas Bird Count trends, sample sizes (n), 95% confidence intervals (CI), significance levels (P),
and relative abundance (RA) for the Burrowing Owl in areas with sufficient data for analysis, 1959-1988
(Sauer et al. 1996).
State Trenda n 95% CI P RAb
Arizona 0.2 16 –1.7 2.1 >0.10 0.10
California –1.2 97 –2.3 –0.1 ≤ 0.05 0.29
Texas 1.2 52 –1.3 3.8 >0.10 0.23
Survey-wide 0.2 240 –1.5 1.9 >0.10 0.13
a–Mean percent change per year.
b–Mean number of birds per 100 party hours.
16 Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Field-based, quantitative population estimates do
not exist for most states (Table 4). However, James
and Espie (1997) submitted surveys to state
biologists in 1992 to determine approximate total
breeding populations of Burrowing Owls, based on
expert opinion and not necessarily based on field
investigations of true population levels. Additional
population estimates have been made for California,
Colorado, Kansas, Montana, and Oklahoma
(Table 4).
Other Surveys, Canada—Burrowing Owls declined
in Canada from the mid-1970s through at least the
early 1990s (Kirk et al. 1994/95) with up to 50%
declines in some areas (Dundas and Jensen 1994/95).
No complete censuses have been conducted in
Canada, but a variety of studies show widespread
range contraction and declining density (Hjertaas et
al. 1995). Burrowing Owls declined in Alberta,
Saskatchewan, and Manitoba at over 20% per year
over the past decade (Wellicome and Holroyd 2001).
Skeel et al. (2001) documented a 95% decline in
Burrowing Owls reported by landowners in
Saskatchewan for an average annual decline of 21.5%
from 1998-2000. They are effectively extirpated from
Manitoba with one pair nesting every second year
since 1999 (K. De Smet, pers. commun.). Shyry et al.
(2001) reported a significant decrease in the density
of Burrowing Owl nests near Hannah, Alberta
between 1991 and 2000. The density of nests near
Brooks, Alberta did not significantly change from
1991 to 2000.
Based on a survey of biologists, the total breeding
population for Canada was estimated as
approximately 2,000-20,000 pairs, with the major
populations occurring in Alberta and Saskatchewan
(Table 4) (James and Espie 1997). In Alberta, the
population estimate dropped from 1,500 to 800 birds
(47% decline) from 1978-1990 (Wellicome 1997).
Other Surveys, Mexico—Burrowing Owls breed in
much of Mexico but the population is unknown. In
nw. Chihuahua they occurred on 62% (n = 34) of
surveyed prairie dog colonies for a total of 87 owls.
Numbers ranged from 0-16 owls/prairie dog colony
and 0.00-7.69 owls/ha (VerCauteren et al. In review).
Two BBS routes in the same area of nw. Chihuahua
average 19 and 32 Burrowing Owls per route
between 1998 and 2001. As many as 26 adults were
visible from a single point on one occasion (W. Howe,
pers. commun.).
Densities
In Nebraska, total numbers of Burrowing Owls
increased, but density decreased with increasing size
of prairie dog towns (Desmond and Savidge 1996). In
large (>35 ha) prairie dog towns, distribution was
found to be less dense but clumped, and clumping
was not related to burrow availability (Desmond et
al. 1995). Burrowing Owl density in black-tailed
prairie dog colonies was negatively correlated with
the density of inactive burrows (Desmond 1991). The
density of Burrowing Owls in prairie dog colonies in
ne. Colorado was positively related to the
percentage of active burrows (Hughes 1993). At least
50% of the burrows were active in 26 of 27 occupied
colonies. For prairie dog colonies with over 90%
active burrows, mean density was 2.85 owls/ha, and
for those with 70-80% active burrows, mean density
was 0.57 owls/ha.
Changes in Breeding Season
Distribution
United States—The Burrowing Owl has been nearly
extirpated from all former breeding range in w.
Minnesota, most areas east of the Missouri River in
North Dakota, e. Nebraska and Oklahoma, e. and c.
Kansas, in large portions of the San Francisco Bay
area in California, and in the Rogue Valley in sw.
Oregon (DeSante et al. 1997, Martell et al. 2001,
Murphy et al. 2001, Sheffield and Howery 2001,
Wellicome and Holroyd 2001).
In California, the Burrowing Owl has been
extirpated as a breeding species during the last 10-15
years from approximately 8% of its former range (J.
Barclay, pers. commun.). They were apparently
extirpated as breeding birds during the past decade
from Sonoma, Marin, Santa Cruz, and Napa
counties, and only one breeding pair apparently still
existed in San Mateo County in 1991. The population
around the north end of San Francisco, San Pablo,
and Suisun Bays was also reduced to a very small
remnant. Breeding in central California has been
reduced to only three isolated populations: a
moderate but declining population of about 720 pairs
in the Central Valley; about 143 pairs in the lowlands
around the southern arm of San Francisco Bay
between Alameda and Redwood City; and a very
small, isolated population of about 10 pairs in the
Livermore area (DeSante et al. 1997).
In a comparison with historical distributions,
Murphy et al. (2001) found that Burrowing Owls
were greatly reduced or completely extirpated from
nw. and c. North Dakota. Declines in Burrowing
Owls may be related to loss of grassland habitat and
burrowing rodents in the state (Murphy et al. 2001).
Populations 17
Table 4. Burrowing Owl population estimates for states, provinces, and countries. James and Espie (1997)
surveyed state/provincial biologists in 1992 to determine approximate total breeding populations. Other
populations estimates are presented only for statewide/province-wide estimates; additional local population
estimates can be found in Appendix A: State Summaries of Burrowing Owl Status.
Area James and Espie (1997)a Other statewide/province-wide estimates (source)
United States 20,000–200,000
Arizona 100–1,000 None
California 1,000–10,000 9,266 pairs (1991–1993; DeSante et al., unpubl.)
Colorado 1,000–10,000 15,796–20,408 individuals (Hanni 2001)b
Idaho 1,000–10,000 None
Iowa <10 None
Kansas 100–1,000 1,000–10,000 pairs (W. Busby, pers. commun.)
Minnesota <10 None
Montana 100–1,000 644 + 114 pairs (Atkinson 2000)c
300 pairs (Holroyd and Wellicome 1997)
Nebraska 100–1,000 None
Nevada 1,000–10,000 None
New Mexico 1,000–10,000 None
North Dakota 100–1,000 None
Oklahoma 100–1,000 800–1,000 individuals (Sheffield and Howery 2001)
Oregon 1,000–10,000 None
South Dakota 100–1,000 None
Texas >10,000 None
Utah 1,000–10,000 None
Washington 100–1,000 None
Wyoming 1,000–10,000 None
Canada 2,000–20,000
Alberta 1,000–10,000 800 birds (in 1990; Wellicome 1997)
British Columbia <10 <10 pairs (Leupin and Low 2001)
Manitoba 10–100 10–20 pairs (K. De Smet, pers. commun.)
Saskatchewan 1,000–10,000 None
Mexico Unknown
a–numbers of breeding pairs
b–estimates are only for e. Colorado, which represents the majority of breeding habitat in the state.
c–estimate is based on surveys of known prairie dog colonies.
18 Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
In w. Minnesota, Burrowing Owls were considered
common in the 1920�����s; however, significant declines
had occurred by the 1960’s (Martell et al. 2001).
During 1965-1985 only 10 breeding records were
recorded. A reintroduction program was attempted
from 1986-1990; however no successful nesting has
been recorded since 1992.
Canada—The Burrowing Owl has been extirpated
from the northern portions of the range in
Saskatchewan and Alberta, and all former range in
Manitoba and British Columbia (Wellicome 1997,
Shyry et al. 2001, Wellicome and Holroyd 2001).
Extirpation from all of Canada may occur within a
few decades (Wellicome and Haug 1995).
Mexico—Unknown.
Re-occupancy Rates
Of 292 nest burrows that had been occupied in some
previous year (1976-83), 39.4% were re-occupied in
Idaho in some subsequent year (up to seven years
later) (Rich 1984). Burrows in rock outcrops were re-used
48.9% of the time (n = 113) compared to 31.4%
(n = 159) for nests in soil mounds. Outcrop sites also
were used more often in consecutive years; 23 were
used for two years, and 12 were used for three
consecutive years. Fifteen mound nests were used
for two years, five were used for three years, and one
was used four consecutive years. Greater reuse of
outcrop sites could be related to their stability as no
burrows in outcrops were destroyed. However, nests
in old badger burrows were destroyed by plowing,
cattle trampling, drifting sand, dredging, and other
unknown causes (Rich 1984).
In Colorado, 90% of 18 prairie dog towns and 25% of
four nesting burrows were reused between 1990 and
1991 (Plumpton and Lutz 1993). In sc. Idaho in 1994-
95, 50% (n = 30) of individual burrows were reused
in a subsequent year (Belthoff and King 1997). Of 10
burrows that fledged young in 1994, 70% were
reused at least once. Conversely, burrows tended to
remain unoccupied in years following nest failures;
six nests remained unused in 1995 and 1996 after
failing in 1994 (Belthoff and King 1997). In sw. Idaho,
low nest reoccupancy was documented (11% from
1991 to 1994, and 42% from 1993 to 1994) (Lehman et
al. 1998).
Korfanta et al. (2001) estimated 17% reoccupancy
(range: 8-28%) of historic breeding sites in e.
Wyoming. The average age of sites reoccupied by
Burrowing Owls in 1998 (12.4 years; n = 10) was not
significantly different from the average age of all
historic observations (13.1 years, n = 86) (Korfanta
et al. 2001). In 1999 and 2000, the Rocky Mountain
Bird Observatory (RMBO) conducted extensive
roadside surveys of potential Burrowing Owl habitat
in se. Wyoming. In 1999, they located 71 colonies of
Burrowing Owls, totaling 180 individuals (Hutchings
et al. 1999). In 2000, they located 107 sites with
Burrowing Owls for a total of 575 owls; site
reoccupancy was 66% between 1999 and 2000 (T.
VerCauteren, pers. commun.).
Populations 19
Range-wide Surveys
There are no ongoing or standardized large-scale
monitoring programs that target Burrowing Owls in
the United States or Canada other than the BBS and
CBC. These surveys do not adequately sample this
species throughout its range (Sauer et al. 2002).
There are no range-wide monitoring programs in
Mexico.
Local Surveys
In Wyoming, Burrowing Owls are voluntarily
reported by state and federal biologists, researchers,
Audubon Society members, and the general public to
the Wyoming Game and Fish Departments (WGFD)
Wildlife Observation System (WOS) (Korfanta et al.
2001).
The New Mexico Burrowing Owl Working Group
(NMBOWG) has initiated a volunteer monitoring
system to collect data on Burrowing Owl populations
in the state (C. Finley, pers. commun.).
In e. Colorado, w. Nebraska, w. Kansas, and e.
Wyoming, RMBO conducts monitoring of prairie
birds, including Burrowing Owls. The objectives are
to investigate trends in population and distribution,
and to determine local densities of birds
(T. VerCauteren, pers. commun.).
Manitoba monitors Burrowing Owl populations
through its Threatened Grassland Birds Project
(Dundas and Jensen 1994/1995). Monitoring in
Saskatchewan and Alberta is conducted through
Operation Burrowing Owl (Dundas and Jensen
1994/1995).
Proposed Protocols and Surveys
In California, the California Burrowing Owl
Consortium has developed Survey Protocol and
Mitigation Guidelines to survey Burrowing Owl
populations and to evaluate impacts from
development projects. The following web site has
the survey protocol and mitigation guidelines
(http://www2.ucsc.edu/scpbrg/section1.htm).
In Wyoming, the Arizona Coop. Fish & Wildlife
Research Unit conducted standardized population
surveys for nesting Burrowing Owls on public lands.
The objectives of this project were to determine the
factors that influence burrow occupancy, nesting
productivity, burrow fidelity, natal recruitment,
conduct an annual survival in Wyoming, and to
provide a paired comparison between tape and
passive surveys in number of birds detected
(C. Conway, pers. commun.).
20 Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Monitoring Activities
Habitat: Breeding
Habitat Loss and Fragmentation—Primary threats
across the North American range of the Burrowing
Owl are habitat loss and fragmentation primarily
due to intensive agricultural and urban development,
and habitat degradation due to declines in
populations of colonial burrowing mammals (Grant
1965, Konrad and Gilmer 1984, Ratcliff 1986, Haug et
al. 1993, Dundas and Jensen 1994/95, Rodriguez-
Estrella et al. 1998, Sheffield 1997a, Dechant et al.
1999). The dramatic reduction of prairie habitat in
the United States has been linked to reduction of
Burrowing Owl populations (Sheffield 1997a).
Fragmentation and isolation may be threats to small
and localized populations. Fragmentation of nesting
habitat may reduce the opportunity for unpaired
owls to find mates (Sheffield 1997a). Fragmentation
of grassland habitat in Canada has increased the
populations of predators that prey on Burrowing
Owls (Wellicome and Haug 1995). In contrast, in
w. Nebraska landscapes dominated by croplands,
Burrowing Owls had higher fledging success
(mean of 3.23 fledglings/pair) than owls nesting in
rangeland landscapes (mean of 1.49 fledglings/pair)
(Desmond 1991). Larger home ranges have been
observed in fragmented landscapes (Warnock and
James 1997). Higher post-fledging mortality from
vehicle collisions occurred in an agricultural
landscape with >90% of land area under cultivation
compared to an unfragmented rangeland with <20%
cultivation (Clayton and Schmutz 1997).
Burrows—Elimination of burrowing rodents
through control programs has been identified as the
primary factor in the recent and historical decline of
Burrowing Owl populations (Butts and Lewis 1982;
Pezzolesi 1994; Desmond and Savidge 1996, 1998,
1999; Toombs 1997; Dechant et al. 1999; Desmond et
al. 2000; Murphy et al. 2001). Some black-tailed
prairie dog colonies have become so isolated through
fragmentation that re-population through natural
dispersal and colonization is difficult (Benedict et al.
1996). Declines of Burrowing Owl populations in
North Dakota north and east of the Missouri River
may be related to declines in Richardson’s ground
squirrel populations (Murphy et al 2001). In w.
Nebraska, a 63% decline in Burrowing Owl numbers
over a seven year period in 17 black-tailed prairie
dog colonies was associated with declines in black-tailed
prairie dog densities due to population control
activities (Desmond et al. 2000). Burrow habitat in
abandoned prairie dog towns becomes unsuitable
for Burrowing Owls within one to three years
(Butts 1973).
Grazing—Burrowing Owls prefer grasslands
moderately or heavily grazed by cattle or prairie
dogs (James and Seabloom 1968, Butts 1973,
Wedgwood 1976, MacCracken et al. 1985, Bock et al.
1993). The response of Burrowing Owls to cattle
grazing is related to the effects of prairie dog
grazing and must be evaluated in conjunction with
the presence of previously excavated burrows. In sc.
Saskatchewan, heavily grazed, poor soils were used
frequently by Burrowing Owls, and moderate to
heavy grazing on good soils reduced lush vegetative
growth and provided suitable habitat (Wedgwood
1976). Burrowing Owls in Saskatchewan and Alberta
nested in pastures with shorter vegetation than
occurred in randomly chosen pastures, and
preferred native or tame pastures over cultivated
land (Clayton 1997). In the Oklahoma Panhandle,
Butts (1973) suggested that grazing of taller grasses
may attract ground squirrels and prairie dogs, thus
increasing burrow availability. In North Dakota,
Burrowing Owls nested in moderately or heavily
grazed mixed-grass pastures, but not in hayed or
lightly grazed mixed-grass (Kantrud 1981). Declines
in Burrowing Owl populations in North Dakota
north and east of the Missouri River may be due to a
reduction over the past 20 years in the amount of
sheep grazing that occurs in the region (Murphy et
al. 2001). In the Platte River Valley of Nebraska,
preferred nest sites were in heavily grazed or
mowed native grasslands (Faanes and Lingle 1995).
Optimal breeding habitat in portions of Colorado,
Montana, Nebraska, North Dakota, South Dakota,
and Wyoming occurred in heavily grazed areas with
aridic ustoll soils and grazed areas with typic boroll
soils (Kantrud and Kologiski 1982).
Burning—Little information exists on the
response of Burrowing Owls to burning. In nc.
Oregon, they were observed nesting in badger
excavations in areas that recently had been burned,
suggesting that fire may create suitable habitat by
reducing vegetation around potential nest sites
(Green and Anthony 1989). In nw. North Dakota,
post-European settlement fire suppression may be
responsible for the development of a taller, denser,
and woodier plant community than previously
existed (Murphy 1993), and these vegetational shifts
may have been responsible for the local extirpation
of Burrowing Owls.
21
Threats
Mowing—In nc. Colorado, mowing has been used to
control growth of grasses and woody vegetation in
areas where black-tailed prairie dogs have been
eliminated. Abandoned black-tailed prairie dog
colonies that were not mowed were not used by owls
(Plumpton 1992). Mowing also may enhance the
attractiveness of nest sites for Burrowing Owls
returning from the wintering grounds (Plumpton
and Lutz 1993). Mowing throughout the breeding
season apparently does not adversely affect nesting
Burrowing Owls (Dechant et al. 1999).
Habitat: Winter
Threats to Burrowing Owl wintering habitats are
largely the same as those to Burrowing Owl
breeding habitats; however, documentation and
research addressing these threats is much more
limited for wintering habitats. VerCauteren et al. (In
review) reported poisoning of prairie dogs, urban
development, and agriculture as the primary threats
to prairie dogs and Burrowing Owl habitat in winter.
Approximately 50% of the prairie dog colonies
resurveyed by VerCauteren et al. (In review) were
extant, although many of the remaining towns were
greatly fragmented.
Overutilization for Commercial,
Recreational, Scientific, or
Educational Purposes
Not known to be a threat. Burrowing Owls have
been trapped and sold in Mexico (G. Holroyd, pers.
commun.), although the extent of this practice is
unknown.
Predation and Disease
Predation—Cultivation and fragmentation of
grassland habitat in Canada have allowed
populations of predators that prey on Burrowing
Owls to increase (Wellicome and Haug 1995).
Burrowing Owls are usually tolerant of human
activity but vulnerable to predation by dogs and
cats. In Minnesota, high predation rates played a
role in the failure of four years of reintroduction
efforts (Martell et al. 2001). On Santa Barbara
Island, California, a small population of Burrowing
Owls (approx. 20) were extirpated by Barn Owls in
1984 and again in 1987 following crashes in the deer
mouse population (Drost and McCluskey 1992).
Disease—Not known to be a direct threat (see
Indirect Effects of Disease, below).
Inadequacy of Existing Regulatory
Mechanisms
Burrowing Owls are protected by the Migratory
Bird Treaty Act (1918) in the United States and
Mexico, which makes it illegal to take, possess,
buy, sell, purchase, or barter any migratory bird
listed in 50 C.F.R., Part 10. In the United States, the
Burrowing Owl was listed as an ESA Category 2
Candidate species until February 1996, when the
Category 2 designation was discontinued.
Burrowing Owls are listed as Endangered in
Canada and as Threatened in Mexico.
Other Natural or Manmade Factors
Disturbance at Nest and Roost Sites—Not known
to be a threat.
Ingestion of Plastics, Lead, Etc.—Not known to be
a threat.
Collisions with Stationary/Moving Structures—
Little information. No Burrowing Owl mortality
due to collisions with communication towers was
documented (Shire et al. 2000). Burrowing Owls
may be susceptible to collisions with vehicles
because Burrowing Owls often fly low to the
ground. Collisions with vehicles have been cited
as a significant source of mortality by several
researchers (Haug et al. 1993). Military aircraft have
been involved with strikes to Burrowing Owls in e.
New Mexico (W. Howe, pers. commun.). Gillihan
(2000) documented a Burrowing Owl killed by a
collision with a barbed wire fence.
Shooting, Trapping, and Hunting—Illegal shooting
may be responsible for substantial mortality in some
areas, accounting for 10 of 15 deaths in Oklahoma
(Butts 1973). Other studies, however, have not
mentioned shooting as a source of mortality
(Coulombe 1971, Thomsen 1971, Martin 1973).
Population Size and Isolation—Johnson (1997)
reported that a population of Burrowing Owls in
California showed a higher genetic similarity than
did a collection of geographically separated
Burrowing Owl populations. This suggested that
some potentially detrimental inbreeding was
occurring in the population (Johnson 1997). However,
Korfanta (2001) found that populations of Burrowing
Owls were genetically indistinguishable, suggesting
a high degree of population connectivity and
dispersal among populations.
Introduced Species—Not known to be a threat.
Indirect Effects of Disease—Burrowing Owl
populations can be negatively impacted, and even
eliminated, by epizootics of sylvatic plague that
affect prairie dog colonies and thus reduce available
habitat for Burrowing Owls (Dechant et al. 1999).
22 Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Pesticides and Other
Contaminants/Toxics
Based on a survey of biologists, eleven states and
provinces reported pesticides as a potential factor in
declines (James and Espie 1997). Use of insecticides
and rodenticides in Burrowing Owl habitat can be
especially detrimental. Pesticides not only reduce
the food supply and the number of burrowing
mammals, but these chemicals also may be toxic to
Burrowing Owls (Ratcliff 1986, James and Fox 1987,
James et al. 1990, Baril 1993, PMRA 1995, Hjertaas
1997a, Sheffield 1997b). Burrowing Owls have been
reported to ingest poisoned rodents and to forage on
the ground for insects in areas with poison grains
also on the ground (Butts 1973, James et al. 1990). In
s. Saskatchewan, owls in pastures treated with
strychnine-coated grain weighed less than those in
control pastures, suggesting a sublethal effect or a
reduction in small-rodent prey (James et al. 1990). A
breeding population in the Oklahoma Panhandle
declined by 71% within one year after sodium
fluoroacetate (1080) was applied to the prairie dog
colony with nesting owls (Butts 1973). Burrows
occasionally are fumigated and sealed in the course
of rodent-control programs (Butts 1973). Anti-coagulant
rodenticides (e.g., brodifacoum and other
second generation [or super-warfarin] compounds)
and other types of rodenticides (e.g., strychnine)
have been shown to cause mortality in many
different owl species, with the ingestion of as few as
one poisoned prey item (Sheffield 1997b). Burrowing
Owls located in proximity to strychnine-coated grain
used to control Richardson’s ground squirrels were
found to have significantly decreased adult body
mass and slightly decreased breeding success as
compared to control owls (James et al. 1990).
Burrowing Owls are known to scavenge dead
rodents and other prey items on occasion, making
them highly susceptible to secondary poisoning by
insecticides and rodenticides (Sheffield 1997b).
There have been few studies examining exposure
and effects of insecticides on Burrowing Owls;
however, available evidence indicates that anti-cholinesterase
insecticides can negatively impact
Burrowing Owl populations (Sheffield 1997a, b). In
Saskatchewan, reproductive output of Burrowing
Owls was not diminished significantly by one or
more exposures to carbaryl within 50 or 400 m of the
nest burrow; however, spraying of carbofuran within
50 m of the nest burrow caused a 54% reduction in
the number of young per nest (James and Fox 1987).
When both carbaryl and carbofuran were sprayed
within 400 m of the nest, productivity of pairs
decreased about 35% more than when carbaryl alone
was applied. Direct overspray of carbofuran to the
nest burrow resulted in an 83% reduction in brood
size and an 82% reduction in nesting success (James
and Fox 1987, Fox et al. 1989). Carbofuran
application within 50 m of the nest burrow, without
direct overspray, resulted in a 17% reduction in
brood size and a 27% reduction in nesting success
compared with burrows exposed to carbaryl or
chloropyrifos. Use of granular formulations of
carbofuran is restricted in the United States and
Canada (PMRA 1995; L. Cole and P. Mineau, pers.
commun.), as is most of its liquid formulations in
Canada (PMRA 1995). Liquid carbofuran is still
registered for several uses in the United States, and
of particular danger to the Burrowing Owls are uses
of this chemical in corn and alfalfa fields (Dechant et
al. 1999).
Burrowing owl populations in California were
sampled for contaminants in the spring of 1996 in the
San Joaquin Valley (Lemoore Naval Air Station
[NAS]), the Imperial Valley (Sonny Bono Salton Sea
National Wildlife Refuge [Salton Sea NWR]), and
Carrizo Plain Natural Area (Gervais et al. 2000).
Sites were representative of the general agricultural
practices in the region; the Carrizo Plain site was a
large native grassland. Eggs, blood, feather, and
footwash samples were collected from Lemoore
NAS and Carrizo Plain, and eggs were collected
from Salton Sea NWR. Eggshells from 45 owl nests
collected prior to 1937 were obtained from the
Western Foundation of Vertebrate Zoology and
measured. Eggshell thickness declined 20.58% from
Burrowing Owl eggs collected prior to 1937
compared to those collected in 1996. In addition, the
eggs from Lemoore NAS were significantly thinner
than those from the Salton Sea NWR or Carrizo
Plain and contained high concentrations of DDE,
ranging from 1.5 to 33 ppm wet weight. Carrizo Plain
and Salton Sea NWR eggs contained up to 0.38 and
3.4 ppm DDE, respectively. Feathers from owls
nesting at Lemoore NAS also contained levels of
DDE, suggesting recent and local exposure. Two
Lemoore eggs also contained PCB. Selenium
concentrations in eggs were at low concentrations
typical of uncontaminated eggs. Footwash samples
indicated exposure to the organophosphorus
pesticide chlorpyrifos at Lemoore NAS, although no
exposure was reported within 1 km of the Burrowing
Owl burrows in the months prior to sampling
(Gervais et al. 2000). Despite the fact that DDT was
banned in 1972, its degradation product DDE clearly
remains a threat to wildlife within the San Joaquin
Valley. Contaminant loads in these owls also may
make them more susceptible to other unrelated
stresses, such as weather or exposure to other
toxicants (e.g., dicofol), that have similar estrogenic
effects as well as thinning effects on eggshells
(Gervais et al. 2000).
Threats 23
Data for Western Burrowing Owls in most of the
U.S. are insufficient to estimate trends in
abundance. Limited data suggest that they are
decreasing in some areas, but may be stable or
increasing in others. Overall, BBS data (which are
reasonably reliable when sample size is adequate)
suggest a long-term decline (-1.5%/yr for the U.S.),
but this estimate is not statistically significant; the
95% confidence interval for the trend estimate is
between –6.5%/yr and +3.6%/yr. Western
Burrowing Owls have experienced significant
population declines at the northern, western, and
eastern fringes of their range, including some local
extirpations; however, they continue to occupy the
majority of their historical range. Primary threats
are habitat loss due to anthropogenic activities,
reductions in abundances of burrowing mammals,
and contaminants.
Currently, the Western Burrowing Owl is listed by
the USFWS as a Bird of Conservation Concern-2002
in most of the BCR’s in which it occurs, in every
USFWS Region where it occurs, and on the National
list (U.S. Fish & Wildlife Service 2002). This
designation is intended to stimulate collaborative,
proactive conservation actions among public and
private land managers and others. Recommended
conservation measures include efforts to monitor
their demographics and trends more precisely, and
to understand the factors affecting their populations
during migration and winter. Conservation efforts
should focus on protection of suitable habitats in
desert, grassland, and shrub-steppe environments.
Additional conservation efforts should focus on
determining the status of Burrowing Owls in Mexico
and on reversing the declines and local extirpations
in the Great Plains and Canada. The conservation of
burrowing mammals is essential to improve the
status of Burrowing Owls, and the listing of the
black-tailed prairie dog as a Candidate species
should assist in the conservation of both species.
The Migratory Bird Management program of the
USFWS recommends retaining the Western
Burrowing Owl on the BCC lists on which it
currently appears. The listing of the Burrowing Owl
as a Bird of Conservation Concern highlights its
potential vulnerability and need for increased
monitoring and conservation attention by multiple
Federal and State agencies and private
organizations. The success of these efforts will be
reviewed as the Birds of Conservation Concern list
is revised.
24 Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Recommendation on
Current Conservation Status
Habitat
Habitat Features—Large, contiguous areas of
treeless, native grasslands should be maintained
(Warnock 1997, Warnock and James 1997, Clayton
and Schmutz 1999). However, because Burrowing
Owls forage over tall grass and nest and roost in
short grass, a mosaic of grassland habitats are
important and a patchwork of reserves with
sustainable land uses in nesting and buffer areas is
recommended (Clayton and Schmutz 1999).
Standardized mitigation protocols to minimize
impacts from developments and disturbances should
be developed (Holroyd et al. 2001). Government
programs and policies that impact Burrowing Owl
habitat should be reviewed to ensure that land-use
changes have positive effects on Burrowing Owl
populations and habitats. Furthermore,
management plans for public lands should include
issues relative to the conservation of Burrowing
Owls, fossorial mammals, and their associated
habitats (Holroyd et al. 2001).
The following management recommendations are
from the Columbia Basin in Oregon (Green and
Anthony 1997): (1) Provide elevated perches near
potential nest burrows in grassland areas if the
average vegetation height is 5-15 cm; (2) Provide
fresh cattle dung near nesting areas if dung is not
available and mammalian predators, especially
badgers, occur in the area. Burrowing Owls use
shredded manure to line their nests and burrow
entrances, possibly to mask nest odors as a
predator-avoidance strategy (Haug et al. 1993,
Dechant et al. 1999). In nc. Oregon, 72% of 32
successful nests were lined with manure, whereas
only 13% (n = 15) of depredated nests were lined
with manure; (3) Place artificial nest boxes no closer
together than 110 m; (4) Construct boxes with width
and length dimensions of at least 36 cm and place
soil around the inside wall; or construct boxes with
only three walls, with a funnel-shaped tunnel
entrance; and (5) Select sites for establishing or
increasing nest sites that have approximately 55%
(40-70%) bare ground and average shrub coverage of
<15%.
Fire—Fire may create suitable habitat by reducing
vegetation around potential nest sites (Green and
Anthony 1989). Post-settlement fire suppression may
be responsible for the development of a taller,
denser, and woodier plant community than
previously existed in North Dakota (Murphy 1993).
Mowing—To encourage Burrowing Owl use in areas
where black-tailed prairie dogs and other grazers
have been eliminated, mowing may be used to
control growth of grasses and woody vegetation.
Abandoned black-tailed prairie dog colonies that
were not mowed were not used by owls (Plumpton
1992). Mowing also may enhance the attractiveness
of nest sites for Burrowing Owls returning from the
wintering grounds (Plumpton and Lutz 1993).
Mowing throughout the breeding season in mid- to
late summer apparently does not adversely affect
nesting Burrowing Owls (T. Wellicome, pers.
commun.). Mowing can maintain abandoned prairie
dog colonies at an early successional stage, with
short (<8 cm) vegetation (Plumpton 1992, Plumpton
and Lutz 1993). Mowing abandoned colonies may be
effective in the short term; however, burrows may
require maintenance by prairie dogs to remain
suitable for Burrowing Owls (MacCracken et al.
1985, Desmond and Savidge 1999).
Grazing—Livestock grazing may be used to
maintain abandoned prairie dog colonies where
native burrowing mammals have been eliminated.
Heavy grazing on saline, gravelly, stony, or sandy
areas and moderate to intense grazing on fertile soils
could create suitable habitat that otherwise would
support tall vegetation (Wedgwood 1976). However,
the effect of grazing on Burrowing Owl habitat and
populations is unknown.
Burrowing Mammals
Conservation of those species of burrowing
mammals that form Burrowing Owl nest sites is
essential for maintaining populations of Burrowing
Owls. Some populations of black-tailed prairie dogs
are in danger of local extirpation, and their colonies
may have become so isolated that re-population
through natural dispersal and colonization is
unlikely (Benedict et al. 1996). Fragmentation and
isolation of habitat patches are potentially important
factors in the decline of black-tailed prairie dog
populations (Dechant et al. 1999). Burrows may
require maintenance by prairie dogs in order to
ensure their long-term suitability for owls and it
may be necessary to release prairie dogs into
inactive colonies (MacCracken et al. 1985, Desmond
et al. 2000). Holroyd et al. (2001) suggested the
expansion of prairie dog colonies on public lands, and
the development of economic incentives to make it
profitable to maintain prairie dog populations on
private lands.
25
Management and
Conservation
Regulation of poisoning and shooting of prairie dogs,
particularly on public lands, may be necessary
(Benedict et al. 1996, Toombs 1997). If lethal control
of burrowing mammals is necessary, restricting the
timing of control activities to avoid the period when
Burrowing Owls choose nest sites or are nesting is
recommended (Butts 1973). Traps, poisoned meat, or
poisoned grain should not be used for rodent control,
but rather burrows unoccupied by owls should be
fumigated (Butts 1973, Thomson 1988). However,
fumigation may have negative impacts on other
burrow dependent species. The area of prairie dog
colonies should be increased, possibly by
reintroducing prairie dogs where they have been
eliminated or by releasing additional prairie dogs
into active colonies to promote colony expansion
(Pezzolesi 1994, Toombs 1997). It is particularly
important to protect colonies ≥ 35 ha in area, which
provide adequate space for nesting Burrowing Owls
(Desmond et al. 1995, Dechant et al. 1999).
Reintroduction and Relocation
Reintroduction—Reintroduction programs have
been attempted in British Columbia, Manitoba,
Minnesota, and Oklahoma with no success. In
British Columbia, an ongoing captive breeding
program reared and released over 140 Burrowing
Owls between 1992 and 1998. Released birds have
raised broods, overwintered at release sites, and
migrated south in winter, but few have returned to
the release site in spring (Leupin and Low 2001,
Munro et al. 1984). In Manitoba, reintroductions
between 1986 and 1996 used a variety of methods,
including the aid of aviaries and artificial burrows,
but resulted in low reproduction and poor return
rates and reintroductions were discontinued
(De Smet 1997). In Minnesota, 105 juveniles were
released in a reintroduction program over four
years, but no successful breeding occurred and the
program was discontinued (Haug et al. 1993, Martell
et al. 2001). Holroyd et al. (2001) recommended a
review of Burrowing Owl reintroduction techniques
and development of new techniques due to failure of
previously used methods.
Relocations and Artificial Burrows—Relocations
are those in which Burrowing Owls are evicted from
their occupied burrows and artificial burrows are
constructed as near to the eviction burrows as
possible to provide acceptable unoccupied burrows
for their use. Ninety percent (n = 6) of artificial
burrows in California were immediately occupied
and these burrows supported successfully breeding
birds for three consecutive years (Trulio 1995).
Artificial burrows were used when they were
approximately 50-100 m from the burrow (Thomsen
1971, Haug and Oliphant 1990). Artificial burrows
more than 100 m from the eviction burrow may
greatly reduce the chances that new burrows will be
used.
The rates of survival and reproduction of Burrowing
Owls relocated to artificial burrows as well as the
long-term use of artificial burrows and the ability of
these burrows to maintain populations are unknown.
The design and installation of artificial nest burrows
should be summarized and the conservation value of
this practice determined (Holroyd et al. 2001).
Follow-up research needs to be conducted to
determine the breeding success of relocated
Burrowing Owls (Holroyd et al. 2001).
Pesticide Use
If insect control is necessary, insecticides with the
lowest toxicity to nontarget organisms should be
used (James and Fox 1987, Fox et al. 1989). Municipal
governments and agricultural representatives
should be encouraged to reduce or restrict the use of
pesticides, and to use pesticides of low toxicity to
nontarget species (Thomson 1988). Pesticides should
not be sprayed within 400-600 m of Burrowing Owl
nest burrows during the breeding season (Haug
1985, Haug and Oliphant 1990, James and Fox 1987).
The possible negative effects of pesticides on
Burrowing Owl populations should be considered on
breeding and wintering grounds (Holroyd et al.
2001).
Monitoring
A standardized, range-wide survey for Burrowing
Owls should be developed and implemented.
Potential survey protocols should be tested to ensure
the quantitative validity of the methodology
(Holroyd et al. 2001). Most current monitoring
programs have problems due to limited coverage or
sample size (see Monitoring Activities, above). A
standardized range-wide roadside survey using call
playback has been recommended. This method was
80% effective at detecting Burrowing Owls using a
15 minute period (five minutes listening, five minutes
call playback, five minutes listening periods), in early
morning and in the early breeding season (Duxbury
and Holroyd 1998). The use of recorded calls can
significantly increase Burrowing Owl detections,
particularly males (Haug and Didiuk 1993). Both
historical sites and areas previously unoccupied by
owls should be monitored. Because of low nest
reoccupancy rates for Burrowing Owls, long-term
monitoring of abundance should not be based solely
on surveys of historical breeding sites (Lehman et
al. 1998).
26 Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Migration
Little information is available. Research projects
conducted by Saskatchewan Environment and
Resource Management and the Canadian Wildlife
Service have attempted to relocate radio-transmittered
Burrowing Owl on their wintering
grounds. Burrowing Owls marked during the
breeding season in Canada (Saskatchewan and
Alberta) have been relocated in s. Texas and c.
Mexico (Veracruz and Michoacan states). Tagged
Burrowing Owls were capable of migrating 200 km
per night, taking at least 2-3 weeks to move from
breeding to wintering grounds. It is estimated that
Burrowing Owls take 6-8 weeks to move from
wintering to breeding grounds
(http://www.serm.gov.sk.ca/ecosystem/speciesatrisk/
burrowingowl.htm, http://members.aol.com/
joemoell/owl2.html, G. Holroyd, pers. commun.).
Wintering Areas
Very little information is available. Although the
general wintering range of Burrowing Owls is
known, very little is known about habitats used
during the winter (Holroyd et al. 2001). Conservation
of Burrowing Owls may depend on acquiring
knowledge about the wintering areas and about
movement patterns, timing, and ecology during
migration and winter. Very few studies have been
carried out in Mexico, Central America, or South
America. The rapid population decline in Canadian
provinces, despite apparent availability of suitable
habitat, suggests unknown factors in winter and
migration may be affecting survival or return rates
(Schmutz 1997).
Education
Private landowners and the general public should be
educated about the status of Burrowing Owls, the
benefits of protecting habitat for the species and for
burrowing mammals, and the negative effects of
insecticides (Butts 1973, James and Fox 1987,
Thomson 1988, Hjertaas 1993, Dechant et al. 1999,
Holroyd et al. 2001). Stewardship of Burrowing Owls
and their habitat should be encouraged on public
land in the United States, Canada, and Mexico
(Holroyd et al. 2001). An educational program should
be developed for schools and outdoor education
programs, and the media should be included in these
activities (Thomson 1988, Holroyd et al. 2001). A
project to improve the public image of prairie dogs
should be undertaken (Benedict et al. 1996, Holroyd
et al. 2001). Operation Burrowing Owl (a private
stewardship program in Canada) has been
extremely successful at obtaining landowner
cooperation in conservation efforts, and has
provided valuable population trend data for
Burrowing Owls in Canada (Hjertaas 1997b). RMBO
and Hawks Aloft, Inc. have also developed successful
education and public participation programs.
Current Activities and Programs
United States—In California, the Burrowing Owl
Consortium, an ad hoc group of biologists and
advocates, meets two times a year. The Consortium
members inform each other and the public of
important issues related to the species, and
subcommittees of the Consortium undertake
projects designed to help the species (L. Trulio, pers.
commun.). The California Burrowing Owl
Consortium prepared the Burrowing Owl Survey
Protocol and Mitigation Guidelines in 1993 to
provide more consistent treatment of impacts to
Burrowing Owls during development projects. This
document was submitted to the California
Department of Fish and Game and became the basis
of their 1995 Staff Report on Burrowing Owl
Mitigation (California Department of Fish and
Game, unpubl. report).
RMBO manages “Prairie Partners”, a program that
requests voluntary cooperation from private
landowners to conserve shortgrass prairie birds and
their habitat through effective stewardship
(Hutchings et al. 1999). In 1999, “Prairie Partners”
documented 468 Burrowing Owl locations (79.3% on
public land). Information is provided to landowners
about shortgrass prairie conservation and
Burrowing Owl natural history. The program also
provides information about landowner attitudes
toward Burrowing Owls and prairie dogs.
RMBO also published ���Sharing Your Land with
Shortgrass Prairie Birds” (Gillihan et al. 2001) which
includes a section on Burrowing Owl identification,
natural history, and habitat requirements and a
booklet focusing on grasslands and grassland birds
for elementary and secondary classroom use
(Hutchings et al. 1999). These materials are being
distributed to landowners, managers, and schools.
The New Mexico Burrowing Owl Working Group
(NMBOWG) was formed in response to population
declines at some sites in New Mexico (Hawks Aloft,
Inc. 2002). The NMBOWG is an volunteer,
collaborative effort of non-profit organizations,
government agencies, private enterprises and
individuals. The working group attempts to
encourage communication, support research, and
facilitate improved Burrowing Owl sighting accuracy
and reporting. The NMBOWG currently supports
on-going research projects at four sites: Holloman
and Kirtland Air Force Bases, New Mexico State
University, and the Turner Ranch. The NMBOWG
has initiated a volunteer monitoring system to
collect data on Burrowing Owl populations in the
state (C. Finley, pers. commun., Hawks Aloft, Inc.
2002).
Management and Conservation 27
Canada—Operation Burrowing Owl is a program
designed to address declines of Burrowing Owls in
Saskatchewan and Alberta. Activities include
increasing public awareness, placing nest boxes,
encouraging voluntary land protection, and
providing monetary incentives to landowners to
protect nesting habitat and avoid pesticide use
around nest sites (Hjertaas 1997b). As of 1993,
several hundred landowners were enrolled in the
project and were protecting over 20,000 ha of
breeding habitat, which supported several hundred
breeding pairs (Dundas and Jensen 1994/95).
Through the Critical Wildlife Habitat Program,
Threatened Grassland Birds Project in Manitoba,
nearly 3,500 ha of critical habitat have been leased or
voluntarily protected for Burrowing Owls and other
grassland species, and over 300 artificial nest
burrows have been installed (Dundas and Jensen
1994/95).
The Canadian Burrowing Owl Recovery Team was
formed in 1989 to coordinate and promote research
and conservation activities to prevent the decline of
this species in Canada. This team meets annually to
review information and to develop and implement
recovery plans. The British Columbia recovery team
has attempted to reintroduce Burrowing Owls into
that province for over a decade. In Alberta, a
provincial recovery team was formed in 2001 to
develop and implement a provincial action plan.
Several organizations conduct public education
programs to increase awareness of Burrowing Owl
conservation issues. The Saskatchewan Burrowing
Owl Interpretive Centre in Moose Jaw was
specifically established to promote awareness of
Burrowing Owl conservation both to visitors and
through extensive school extension programs. The
Alberta Fish and Game Association through their
Operation Grassland Community delivers similar
programs in the province. The Canadian Species at
Risk Habitat Stewardship Program funds non-government
partners to deliver habitat stewardship
projects in all four western provinces which benefit
Burrowing Owls, their habitats and other prairie
wildlife. (G. Holroyd, pers. commun.).
28 Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Coordinated, range-wide research on population
demographics needs to be conducted to determine
causes of populations declines (Holroyd and
Wellicome 1997, Holroyd et al. 2001). Metapopulation
dynamics, influence of landscape patterns, and the
effects of fragmentation and isolation on populations
are not well understood. Basic distribution data and
factors affecting survival during migration and on
wintering grounds are poorly known and may be
important in determining causes of population
declines (Holroyd et al. 2001). A standardized survey
to monitor population trends in Canada, the U.S.,
and Mexico is recommended as many population
estimates are simply based on “best guesses” and
current large-scale monitoring programs are largely
inadequate (Holroyd et al. 2001).
Management strategies currently in use need to be
evaluated for their effectiveness and the resulting
information made easily available to managers.
Further investigations also are needed on land use
impacts, prescribed fire, grazing, mowing, habitat
enhancements (e.g., artificial burrows and perches),
relocation and reintroduction, and impact of
predators on nest success (Millsap et al. 1997,
Sheffield 1997a, Holroyd et al. 2001). Rates of habitat
conversion and degradation (e.g., agricultural
conversion or decline in burrowing mammal
colonies) are rarely reported and more work is
needed to determine rate and extent of habitat loss
(James and Espie 1997). Modeling of Burrowing Owl
habitat selection has been suggested to better
understand the role of anthropogenic factors in
population declines (Holroyd et al. 2001).
Although some research exists on carbofuran,
studies of many other pesticides are also needed
(James and Espie 1997, Holroyd et al. 2001). Indirect
and sublethal effects of pesticides are largely
unknown. The extent of mortality and vulnerability
to shooting, particularly during prairie dog and
ground squirrel control, is generally unknown.
Some education programs have already been
successfully developed and implemented. However,
additional research is needed to determine
landowner and land manager attitudes to Burrowing
Owls and burrowing mammals and to determine
best methods for improving attitudes and
conservation efforts on private and public lands.
29
Research Needs
An extensive bibliography of articles pertaining
to the Burrowing Owl was compiled by L. Ayers.
The bibliography is available on the internet at the
following address: http://uwadmnweb.uwyo.edu/
fish_wild/buow/citations.html
American Ornithologists’ Union. 1998. Check-list of
North American Birds. Seventh Edition.
American Ornithologists’ Union, Washington, DC.
Arrowood, P. C., C. A. Finley, and B. C. Thompson.
2001. Analyses of Burrowing Owl populations in
New Mexico. Journal of Raptor Research 35:362-
370.
Baril, A. 1993. Pesticides and wildlife in the prairies:
current regulatory issues. Pages 44-48 in G. L.
Holroyd, H. L. Dickson, M. Regnier, and H. C.
Smith, editors. Proceedings of the third
endangered species and prairie conservation
workshop. Natural History Occasional Paper 19.
Provincial Museum of Alberta, Edmonton,
Alberta, Canada.
Belthoff, J. R. and B. A. King. 1997. Between-year
movements and nest burrow use by Burrowing
Owls in southwestern Idaho. Technical Bulletin
No. 97-3, Idaho Bureau of Land Management.
Benedict, R. A., P. W. Freeman, and H. H. Genoways.
1996. Prairie legacies—mammals. Pages 149-167
in F. B. Samson and F. L. Knopf, editors. Prairie
conservation: preserving North America’s most
endangered ecosystem. Island Press, Covelo,
California.
Bock, C. E., V. A. Saab, T. D. Rich, and D. S. Dobkin.
1993. Effects of livestock grazing on Neotropical
migratory landbirds in western North America.
Pages 296-309 in D. M. Finch and P. W. Stangel,
editors. Status and management of Neotropical
migratory birds. U.S.D.A. Forest Service,
General Technical Report RM-229.
Botelho, E. S., and P. C. Arrowood. 1996. Nesting
success of western Burrowing Owls in natural and
human-altered environments. Pages 61-68 in D.
Bird, D. Varland, and J. Negro, editors. Raptors
in human landscapes: Adaptation to Built and
Cultivated Environments. Academic Press, Inc.
Brown, N. L. 2001. The howdy owls of Arizona: a
review of the status of Athene cunicularia.
Journal of Raptor Research 35:344-350.
Butts, K. O. 1973. Life history and habitat
requirements of Burrowing Owls in western
Oklahoma. M.S. Thesis. Oklahoma State
University, Stillwater, Oklahoma.
Butts, K. O., and J. C. Lewis. 1982. The importance
of prairie dog towns to Burrowing Owls in
Oklahoma. Proceedings of the Oklahoma
Academy of Science 62:46-52.
Clark, R. J., J. L. Lincer, and J. S. Clark. 1997.
Appendix A: a bibliography on the Burrowing
Owl (Speotyto cunicularia). Pages 145-170 in J.
Lincer and K. Steenhof, editors. The Burrowing
Owl, its biology and management including the
proceedings of the First International Burrowing
Owl Symposium. Raptor Research Report
Number 9.
Clayton, K. M. 1997. Post-fledging ecology of
Burrowing Owls in Alberta and Saskatchewan:
dispersal, survival, habitat use, and diet. M.S.
Thesis. University of Saskatchewan, Saskatoon,
Saskatchewan, Canada.
Clayton, K. M., and J. F. Schmutz. 1997. Burrowing
Owl (Speotyto cunicularia) survival in prairie
Canada. Pages 107-110 in J. R. Duncan, D. H.
Johnson, and T. H. Nicholls, editors. Biology and
conservation of owls of the Northern
Hemisphere. U.S.D.A. Forest Service, General
Technical Report NC-190. North Central Forest
Experiment Station, St. Paul, Minnesota.
Clayton, K. M., and J. K. Schmutz. 1999. Is the
decline of Burrowing Owls Speotyto cunicularia
in prairie Canada linked to changes in Great
Plains ecosystems? Bird Conservation
International 9:163-185.
Coulombe, H. N. 1971. Behavior and population
ecology of the Burrowing Owl, Speotyto
cunicularia, in the Imperial Valley of California.
Condor 73:162-176.
30 Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States
Literature Cited
De Smet, K. D. 1997. Burrowing Owl (Speotyto
cunicularia) monitoring and management
activities in Manitoba, 1987-1996. Pages 123-130 in
J. R. Duncan, D. H. Johnson, and T. H. Nicholls,
editors. Biology and conservation of owls of the
Northern Hemisphere: Second International
Symposium. U.S.D.A., Forest Service General
Technical Report NC-190, North Central Forest
Experiment Station, St. Paul, Minnesota.
Dechant, J. A., M. L. Sondreal, D. H. Johnson, L. D.
Igl, C. M. Goldade, P. A. Rabie, and B. R. Euliss.
1999. Effects of management practices on
grassland birds: Burrowing Owl. Northern
Prairie Wildlife Research Center, Jamestown,
North Dakota. Northern Prairie Wildlife
Research Center Home Page.
http://www.npwrc.usgs.gov/resource/literatr/
grasbird/buow/buow.htm
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for Bird Populations, Point Reyes Station,
California.
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Desmond, M. J. 1991. Ecological aspects of
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Nebraska panhandle. M.S. Thesis. University of
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influencing Burrowing Owl (Speotyto
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Owl conservation in the Great Plains. Page 9 in
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Desmond, M. J., and J. A. Savidge. 1999. Satellite
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grassland birds in the western hemisphere.
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Desmond, M. J., J. A. Savidge, and K. M. Eskridge.
2000. Correlations between Burrowing Owl and
black-tailed prairie dog declines: a 7-year
analysis. Journal of Wildlife Management
64:1067-1075.
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of alternative prey during a small rodent crash.
Oecologia 92:301-304.
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status and conservation. Bird Trends 4:21-22.
Duxbury, J. M., and G. L. Holroyd. 1998. Testing a
possible standardized, road-side survey technique
for Burrowing Owls. Abstract and notes. Second
International Burrowing Owl Symposium, Ogden,
Utah.
Enriquez-Rocha, P. L. 1997. Seasonal Records of the
Burrowing Owl in Mexico. 1997. Pages 49-51 in J.
Lincer and K. Steenhof, editors. The Burrowing
Owl, its biology and management including the
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Faanes, C. A., and G. R. Lingle. 1995. Breeding birds
of the Platte River Valley of Nebraska. Northern
Prairie Wildlife Research Center home page,
Jamestown, North Dakota.
http://www.npwrc.usgs.gov/resource/distr/birds/
platte/platte.htm (Version 16JUL97).
Fox, G. A., P. Mineau, B. Collins, and P. C. James.
1989. The impact of the insecticide carbofuran
(Furadan 480F) on the Burrowing Owl in Canada.
Technical Report Series No. 72. Canadian Wildlife
Service, Ottawa, Canada.
Gervais J. A., D. K. Rosenberg, D. M. Fry, L. J.
Trulio, and K. K. Sturm. 2000. Burrowing owls
and agricultural pesticides: evaluation of residues
and risks for three populations in California,
USA. Environmental Toxicology and Chemistry
19:337-343.
Gillihan, S. W. 2000. Barbed wire fence fatal to
Burrowing Owl. Journal of the Colorado Field
Ornithologists 34:220-221.
Gillihan, S. W., D. J. Hanni, S. W. Hutchings, T.
Toombs, and T. VerCauteren. 2001. Sharing your
land with shortgrass prairie birds. Unpublished
Report. Rocky Mountain Bird Observatory,
Brighton, Colorado.
Gleason, R. S. 1978. Aspects of the breeding biology
of Burrowing Owls in southeastern Idaho. M.S.
Thesis. University of Idaho, Moscow, Idaho.
Gleason, R. S., and D. R. Johnson. 1985. Factors
influencing nesting success of Burrowing Owls
in southeastern Idaho. Great Basin Naturalist
45:81-84.
Literature Cited 31
Grant, R. A. 1965. The Burrowing Owl in Minnesota.
Loon 37:2-17.
Green, G. A., and R. G. Anthony. 1989. Nesting
success and habitat relationships of Burrowing
Owls in the Columbia Basin, Oregon. Condor
91:347-354.
Green, G. A., and R. G. Anthony. 1997. Ecological
considerations for management of breeding
Burrowing Owls in the Columbia Basin. Pages
117-121 in J. Lincer and K. Steenhof, editors. The
Burrowing Owl, its biology and management
including the Proceedings of the First
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