We all know that disheartening sound: a
bird smacking into a window in our house
or office building. The fact that birds strike
our windows every day is not only sad, it's
serious: more birds die because of
collisions with glass than any other factor
associated with human activity. Anywhere
from 100 million to 1 billion birds are killed
by window strikes each year. These strikes
account for the death of up to 5% of the fall
bird population. As the number of our
homes and offices continues to grow, the
number of bird deaths is likely to increase
as well.
Why Do Birds Fly Into Glass?
Windows allow us an opening into the
natural world outside. Unfortunately, the
glass which is a portal for us is actually a
barrier to birds. Both tinted and clear
glass are invisible to birds, who see a plant
or tree in the reflection of a window,
misinterpret it as safe haven, and fly
toward it. The placement of leafy green
plants inside a window seems to increase
the risk of collision. Another hazardous
situation occurs when one pane of glass
faces another, which creates an illusion of a
passageway through a structure. The
extra momentum gathered as the bird
attempts to "pass through" is especially
deadly.
The Danger of Plate Glass
Understanding and Avoiding
That Painful Thud
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 Materials
web - http://www.BirdDay.org
phone - 1-866/334-3330
March 2005
Tall buildings pose a special threat at night
because of their artificial lights, which
attract birds as they migrate. Bird
collisions are especially high during
periods of bad weather, including fog, low
clouds, and rain. Other factors which can
increase the number of birds flying
through urban areas (and crashing into the
glass surfaces there) include strong winds
and sudden changes in temperature.
Glass is dangerous in structures of all
sizes, including homes, schools,
storefronts, offices and apartment
buildings. It is also lethal in every season.
City skyscrapers result in the biggest kills
at night during the spring and fall
migrations, when the lights of tall
structures confuse birds on their flight
path. However, Klem reported that most
birds are actually killed during the day in
winter, when birds are attracted to the bird
feeders set up by approximately 25% of the
North American population.
What Happens When Birds Fly into Glass?
Although the sound of a bird hitting one of
our windows may be a familiar one, the
actual discovery of dead birds lying
beneath our windows is somewhat less
common. The fact that relatively few dead
birds are discovered is misleading,
however, and the resulting belief that most
birds can survive a window strike is false.
Klem estimates that one in two birds who
collide with glass will die as a result.
Typical injuries include broken beaks,
feathers, and head trauma.
The deceptively low numbers of dead birds
found underneath problem windows may
largely be due to the ability of predators
(cats, dogs, raccoons) to quickly seize a
dead or injured bird before we have even
seen it. The decorative shrubs and plants
which surround our homes make their
discovery even more difficult. Birds may
survive the initial impact, fly off to a safe
area, only to later die of injuries sustained
in the collision.
What Can We Do to Keep Birds Safe?
Make glass visible. If birds realize that
the glass barrier exists, they are able to
avoid it. There are different ways to help
birds see glass, ranging from the extreme
(whitewashing, etching or sandblasting) to
the moderate (hanging sun ornaments or
other materials). The popular solution of
hanging hawk silhouettes in windows is less
effective than moving pictures or ribbons.
Specialty products, such as Wing Chimes
and CollideEscape (film which covers a
window while preserving the interior view)
are available at a web site devoted to glass
safety (www.flap.org). Even the simple acts
of closing blinds, drawing drapes, and
turning off lights at night have been proven
effective in reducing window strikes.
Create barriers. A barrier between the
bird and the glass may prevent birds from
colliding. External sun shades and soccer-grade
netting are both effective ways of
keeping birds in flight away from a window.
Consider placement when attracting
birds. People can also make a difference by
putting their feeders and birdbaths in safe
locations. Several studies show that
feeders should be placed either very close
to a window (less than 3 feet) or far away
(more than 30 feet), so that the feeders are
not directly in the birds' flight path when
they fly from the feeder. Using window
feeders prevents birds from gathering
deadly momentum even if they do strike
the glass during their flight.
Explore innovations in new construction.
Windows that are adjusted in angle are
safer in new buildings; studies show that
even a 20 degree angle significantly lowers
bird fatalities. New windows can also be
modified in appearance, such as the glass in
the new observation tower in Niagara Falls
State Park, which has a striped pattern to
help increase its visibility for birds.
Another experiment in such technology is
the Swarthmore project, where builders
are installing panes which use tiny dots of
opaque glass to achieve a semifrosted look.
Support Lights Out Programs. Turning
off lights at night in buildings and homes
prevents the birds from being attracted to,
or confused by illuminated windows. An
example of city-wide success is the "Lights
Out" program voluntarily adopted by most
of the major skyscrapers in Chicago. Since
the buildings began dimming or turning off
lights, bird deaths during migration season
are estimated to have dropped by as much
as 80 percent. Similar programs are being
studied and at least partially implemented
in areas of New York and Toronto.
What Can I Do if a Bird Crashes into my
Window?
Despite our best efforts, birds will continue
to fly into glass in our offices and homes. If
you find a bird that has been killed or
injured by such a collision, you should use a
towel to cover and catch the bird, and place
it in a paper bag or cardboard box that can
be closed or covered securely (be sure to
provide airholes). Keep the contained bird
in a warm, dark and quiet place away from
noise and activity. Check on the bird every
half-hour, but do not handle it. If it seems
to recover, take the container outside and
set the bird free. If it does not recover
within a few hours, contact a wildlife
rehabilitator.
There are several ways to find your
nearest rehabilitator. Contact:
• Your local animal shelter or division of
the Humane Society,
• Your local veterinarian,
• Your state Division of Natural Resources, or
•The National Wildlife Rehabilitators
Association at (320) 259-4086, or the
International Wildlife Rehabilitation
Council at (408) 271-2685.
