Window collisions is one of the three top three
causes for bird decline among North American birds
and may be the number one quantifiable cause (the
other two are habitat loss and cat predation).
Researchers estimate that between one and ten birds
are killed EACH year at EVERY home in the US.
Combined with commercial building kills, between 100
million and a billion birds perish this way each
Birds don't recognize glass the way we do.
They see the reflection of the sky and trees and it
seems like a continuation of the sky to them.
Birds are also attracted to inside vegetation, not
realizing that it is behind glass. Do not think that
a bird has never hit your window if you have not
seen their bodies in your yard. Many birds fly
away, but are gravely injured and later die from the
blunt force trauma of colliding with the glass.
Imprint of bird on window in a private home
A variation of this experience happens with larger
commercial buildings. With both the use of glass in
general, and the use of reflective glass as the
main type, growing in popularity, many glass-facaded
commercial buildings have become significant
sources of bird mortality. This problem is magnified
when trees are planted near the building.
Migrating birds see the reflection as reality, and
seeking the sky or tree the reflection presents,
unwittingly fly into the glass with lethal force.
Unfortunately, it is not unusual for dozens of birds
to perish at problematic buildings as they
navigate on migration through urban centers like New
York, Boston, Chicago, Toronto and San Francisco. Long Island buildings pose a problem too. Fifty two
golden-crowned kinglets, several warbler species and
yellow-bellied sapsuckers died in one day flying
into an all-glass building situated in Great Neck as
they migrated south this past October. All-glass
buildings at the Jericho and Huntington Quadrangles
are also known to kill birds.
small group of dead birds found one morning at an office building in Great Neck in spring 2010.
Fortunately, there is a technological answer to the problem. Unlike humans, birds can see ultraviolet light. Window and window film manufacturers are taking advantage of this ability by making windows and easily applied window films that reflect UV light. Windows so equipped, instead of deceiving birds, inform them that the windows are solid objects that should be avoided. And since we cannot see UV light these solutions pose no aesthetic concern. For more ways that you can help birds, see below.
Purchase BirdTape for windows from the
American Bird Conservancy
- Because collisions are caused by birds
attempting to fly through glass, or because they
see the reflections of the sky and trees and are
unable to recognize the glass as a solid object,
be sure to break up or eliminate their view by
placing decals on your windows, ideally
one-quarter-inch wide, white, vertical stripes
spaced four inches apart, or one-eighth-inch,
black, horizontal stripes spaced one inch apart.
- If you feed birds in your yard, move the
feeders and bird baths to within three feet of
your window. The birds cannot gain enough
momentum at this close range and you greatly
decrease the chance that they will get hurt. If
this is not possible, move them at least thirty
- Move inside plants away from windows so that
birds do not mistake them for outdoor habitat.
- Consider using screens, bars or film on your
window to eliminate reflections. If you can,
purchase bird safe glass to have installed.
- If you are landscaping your yard, try to
place trees and shrubs away from your windows in
order to prevent reflections in the glass that
look like a continuation of your yard.
Commercial building owners
- Check out
The American Bird Conservancy has produced the
book Bird-Friendly Building Design to assist
developers, architects,and building owners
working with LEED Pilot
Credit #55 – Reducing Bird Collisions;
regulators and builders researching the
application of voluntary guidelines or
mandatory standards for buildings;or anyone
simply looking for detailed information on the
collisions issue and designing structures that
minimize bird deaths.