Perils Past and Present
Major Threats to Birds Over Time
International
Migratory
Bird Day
(IMBD),
held annually
on the second
Saturday in
May, is an
invitation to
celebrate and
support
migratory bird
conservation.
IMBD Information
web - http://birds.fws.gov/imbd
phone - 703 /358-2318
IMBD Sales
web - http://www.BirdDay.org
phone - 1-866/334-3330
January 2003
Of the challenges faced by bird
populations, the majority are related to
human activities. Some of the most
significant threats of the past century
have been overcome due to increased
advocacy for wildlife and the passage of
numerous laws protecting birds and their
habitats. However, major threats persist,
putting numerous species at risk and
requiring our attention and action.
Habitat Loss and Degradation
Past
By 1900, millions of immigrants had
arrived in North America, clearing
forests, draining wetlands, and
converting native grasslands for farming,
grazing and fuel. With widespread
conversion of natural habitat to human
uses, it’s no wonder that many forms of
once-abundant wildlife, such as the wild
Turkey, became scarce in settled areas.
People now generally recognize the
importance of conserving habitat in order
to conserve wildlife. Natural habitat is
protected in the form of Migratory Bird
Sanctuaries and National Wildlife Areas
in Canada; National Wildlife Refuges and
State wildlife management areas in the
U.S., and the System of Protected
Natural Areas in Mexico. In North
America, 2.5 million km2 (618 million
acres) of land, freshwater, and marine
areas – equalling nine percent of the
continent – have been dedicated as
wildlife habitat. Public lands held for
other purposes, such as forestry, grazing,
and even military exercises also set aside
for wildlife, as are millions of acres by
private landowners.
Present
The fact is that despite the areas set
aside for wildlife, some bird populations
are still at risk from habitat loss. Much
of the landscape continues to undergo
degradation and conversion due to human
development and disturbance. We are
still experiencing a net loss of wetlands in
North America, for example. In addition,
growing numbers of birds are killed due
to collisions with human structures and
equipment, including power lines,
communication towers, wind turbines,
glass windows, and automobiles. Our
challenge is to manage landscapes,
control development and alter our
activities in such as way that people and
birds can coexist.
Overexploitation
Past
Wild birds were once sold for food in
restaurants and markets across North
America. All types of birds were
harvested, including shorebirds, seabirds,
even songbirds, in addition to those
considered “game birds” today (such as
ducks, geese, doves, turkeys, pheasants).
Wild birds were also harvested for their
skins and feathers to supply the millinery
(hat making) trade. In 1886, American
Museum of Natural History ornithologist
Frank Chapman surveyed ladies’ hats
during two walks in New York City and
discovered the bodies or body parts of
wild birds on 542 out of 700 hats.
The commercial trade in birds depleted
some species to the point of extinction.
Fortunately, public campaigns, stronger
regulations, and changing fashion
stopped the slaughter. These days, most
birds are under some form of protection.
It’s even illegal to possess most wild bird
feathers without a permit. For species
still harvested, well-regulated hunting
serves as a tool for conservation rather
than a threat.
Present
Some species of birds are still threatened
by commercial exploitation; most notably,
parrots targeted for the exotic pet bird
trade. Trade in wild-caught parrots,
coupled with habitat loss, has resulted in
the parrot family having more globally
threatened species than any other family
of birds. The U.S. used to be the largest
consumer of parrots, legally importing
250,000 mostly wild-caught parrots a
year. This changed with the passage of
the U.S. Wild Bird Conservation Act,
which controls trade in parrots listed
under the Convention on International
Trade in Endangered Species, and with
Mexico’s ban on exporting parrots. The
Act also helped reduce smuggling, but
illegally-caught parrots still flow across
the border. The black market and the
legal trade still occurring in many
countries are cause for great concern.
Consumers should take care to never buy
a wild caught parrot: for every one that
reaches a store, four will have died along
the way.
Present
Birds are still victims of pesticide expo-sure.
Each year, about 67 million birds
die from direct exposure to pesticides on
farmlands in the U.S. An estimated 7
million bird deaths are attributed to
homeowner use of pesticides. These
figures do not include birds that perish
after a period of illness, that die after
feeding on poisoned insects, rodents, or
other prey, or losses due to failed repro-duction
(eggs left unhatched or nestlings
left to starve). The impact on birds from
pesticide use in areas outside the U.S. is
unknown. Exposure is likely to be higher
in Latin American countries where
migratory birds spend their winters and
the permissible types and quantities of
pesticides are less regulated.
Homeowners have many opportunities to
lessen the impacts of pesticides on birds
and minimize bird deaths. Currently,
homeowners use up to 10 times more
chemical pesticides per acre on their
lawns than farmers and spend more per
acre, on average, to maintain their lawns
than farmers spend per acre on crops.
Moreover, a 1992 survey revealed that
more than 63 percent of the households
surveyed had 1 to 5 pesticides in storage.
Homeowners can improve this situation
by practicing pest prevention, planting
native vegetation, encouraging birds to
visit, using non-chemical controls where
possible, and carefully following applica-tion
and disposal instructions.
Introduced Species
Past
Purposefully or accidentally, people have
introduced new plants and animals
around the world, some of which have
proven very harmful to native birds. A
famous intentional introduction was the
1890-91 release of 80 to 100 European
Starlings in New York City by an
organization seeking to introduce to
North America all birds mentioned by
Shakespeare. Starlings proliferated and
now compete with native birds for
nesting sites. Unintentional
introductions occur when new species are
transferred unknowingly or accidentally.
For instance, Black Rats and Norway
Rats from Europe were stowaways on
early ships arriving in the Americas.
Rats prey on many native bird species, as
well as being a serious pest to humans.
Introduced species may adversely affect
native bird populations in ways other
than predation or competition. Intro-duced
herbivores and exotic plants can
degrade habitat quality; other introduced
species serve as carriers of disease. The
effects of introduced species are most
severe on islands, since island-bound
birds such as nesting seabirds or resident
species evolved to be flightless are
especially vulnerable to introduced
species such as rats, snakes, hogs, foxes,
and goats. Ninety percent of historical
bird extinctions have occurred on islands.
Present
Today, numerous regulations and cam-paigns
exist to remove harmful intro-duced
species and prevent new introduc-tions.
For example, authorities in Hawaii
vigilantly search port facilities to avoid
introduction of the Brown Tree Snake,
responsible for the decimation of birds on
Guam. However, some introduced
species are here to stay. In fact, one of
the most dangerous introduced predators
is the domestic cat. Tame and feral cats
kill hundreds of millions of songbirds and
other avian species each year. A study in
Wisconsin estimated that in that state
alone, rural housecats kill roughly 39
million birds annually. Add the deaths
caused by feral cats, or domestic cats in
urban and suburban areas, and this
mortality figure would be much higher.
Responsible cat owners, by spaying and
neutering and keeping cats indoors,
prevent unwanted, uncared-for cats; have
healthier pets; and save the lives of
millions of birds each year.
Pesticides
Past
From the 1940s to 1960s, the pesticide
dichloro-diphenyl-trichloroethane (DDT)
was used in numerous countries to
vanquish malaria and other insect-borne
diseases, saving human lives, and to
control agricultural pests, boosting food
production. Unfortunately, DDT and
many other pesticides were frequently
over-applied and inappropriately used.
DDT and other hydrocarbon pesticides
accumulated in the bodies of birds of prey
via the food chain, affecting eggshell
production and causing nesting failure.
The result was a drastic decline in
Brown Pelicans, Ospreys, Bald Eagles
and other birds of prey. Due to public
outcry, authorities in the U.S. and
Canada banned DDT in the early 1970s
and enacted stronger regulation of
pesticide production and use.
