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BIRD COLUMN FOR SEPTEMBER 5,
2004
By Benjamin P.
Burtt TOPIC: The dangers to birds caused by the
reflections from glass windows. Some are killed by colliding at high speed with the glass while others spend fruitless hours attacking their own reflection visible in a window near their nest. One Billion
Birds are Killed each Year when they Collide
with Windows in the United States. Introduction This column is
divided into two sections here Section 1 contains a copy of the column as it
appeared in the newspaper on the date above. Section 2
contains additional information for the reader who is interested in learning
more about the subject of this column SECTION
1: THIS IS A COPY OF THE COLUMN THAT APPEARED IN THE POST STANDARD ON
SEPTEMBER 5, 2004 The fall migration has startedSparrows that nested further north will pass through
during September and October. Even
now the white-throated sparrow is migrating. Question: Mr. Burtt: Recently, a
bird hit my window and died. Is there some way to prevent this? M.S. Liverpool, NY. Dear M.S.: This happens to a lot of birds as they fly away
from a feeder towards the reflection of the sky or the reflection of the
plants nearby. In addition during the next two months, migrating birds
will also collide with windows on homes that are situated on a migration
route. They collide with the glass on
buildings in our big cities. Birds do not recognize glass as a solid object. Professor Daniel Klem of Muhlenberg College has studied
bird collisions with windows in commercial buildings and homes. It is a very serious environmental problem
and windows kill more birds than any other thing that humans do except our
destruction of their habitat. A conservative estimate indicates that almost a 1 billion birds are killed by glass each year in the U.S. This is about 10 birds per building.
Before the World Trade Center towers were destroyed, about 32 birds were
found dead there per year by volunteers from the NYC Audubon Society. This is
only a fraction of the casualties for many carcasses probably were not found,
or were cleaned up by maintenance. Some undoubtedly were eaten by gulls or
rats.
CAPTION: Thousands of migrating birds are killed by
colliding with windows in the buildings of New York City. The white-throated
sparrow is the most frequent victim found in downtown Manhatten. The arrows in
this painting from Peterson's "Birds of Eastern and Central North
America" call attention to important field marks for identification, the
white throat and the white stripes on the crown. ( Courtesy of Houghton
Mifflin Co.) A number of things have been tried in an effort to
decrease the reflection or to frighten the birds away. There is a new simple method that I think we should try at
our homes. It was invented by Stiles Thomas of New Jersey. One or more lengths of monofilament fishing line are fastened
above the window and extend to the bottom.
Attach a six to seven inch white or colored feather about every 7
inches. Keep the line loose so the feathers can blow back and forth across
the window. I am not sure why it frightens birds, but would you give it a try
and let me know whether it works? You can get feathers at a craft shop or
perhaps from a chicken or turkey farm. Many other methods are worth trying and are discussed in
Section 2 that follows just below. SECTION 2
COVERS THE FOLLOWING MATERIAL THAT DID NOT APPEAR IN THE NEWSPAPER: A. Bird
Collisions with windows and additional methods for preventing
these accidents. B. The
problem of birds attacking their own reflection that they see in a window
near where they are nesting. A.
HIGH SPEED COLLISIONS WITH THE WINDOW. One of the hazards of any window is that it reflects the
garden and sky and birds in flight mistake the reflection as part of the
scenery and fly headlong into the window. Professor Daniel Klem of Muhlenberg College was mentioned
above. Here is more of what he discovered over a 20 year period as he studied
the accidents that befall birds that collide with windows. From his studies he came to the conclusion
that each year, between 100 million birds and 900 million birds are killed by colliding with windows in homes
and buildings, particularly with tall ones in the cities. This is where I
obtained the estimate of the annual window caused deaths of nearly a billion
birds. Often at our homes, a bird that has been at a feeder will
leave it and crash into a window as it heads towards the reflection of the
open sky. Klem has shown that the number of fatalities increases as the
feeder is placed further from the window glass. There were no fatalities if the feeder was located 3 feet or
less from the window. However, birds that hit the window after leaving a more
distant feeder were much more likely to die. If the feeder was 15 feet or more from the glass, over
half of the collisions were instantly fatal. So you can save the lives of
some birds by having your feeder close to the window. You can also better see the birds when
they are close to you! Home owners often report that a particular window kills
many, many birds each year. Such a window usually faces north or south in an
open area where migrating birds are already moving at high speeds. Our large window faces the area where the birds feed. The
house and window form the southern boundary of a clearing in the trees and
shrubs. Our window is not protected by an overhanging roof, so the
room inside is bright and well illuminated. This reduces the intensity of the
reflection. Windows that are underneath the shelter of a roof generally kill
more birds since the reflection is more obvious when the room behind the window is dark. If you are building a house with large windows facing the
garden, you can have the glass tilted downward, that is have the glass lean outward
from the top. Sometimes a building will have large windows designed this way.
A bird flying towards the window does not see a reflection of the sky and
garden, but only the image of the ground below the window and will veer away. Attacking
the window. Here
is another question about birds and windows. Question: Dear Mr. Burtt: A cardinal was flying up against my window last
spring for hours at a time. Is there
some way to stop this if it happens again?
J.B., Hastings, NY Dear J.B.:This question is also related to the fact that
birds do not understand the nature of reflections they see in a nearby
window. The cardinal was attacking
the image that it saw of itself that was reflected by the glass. It instinctively
tries to drive away any other cardinal that comes near to where it plans to
nest. To the annoyance of the homeowner, this thumping against the glass may begin as early as
sunrise. The bird often carries on this activity until it is almost exhausted.
Each bird tries to keep the area around its nest clear of
birds of the same kind. This area, called the territory, varies in size with
different species. With robins for example, it may be from 70 by 70 feet up
to an area 100 feet on a side. If a male bird of the same species enters into that
territory, the resident threatens the intruder. Sometimes there is physical
contact, but more often a threatening rush will send the visitor flying. Having a territory to itself is advantageous to the
resident. It reduces interference by others, it may insure a better food
supply, it spreads birds out and reduces losses due to predation and disease.
If a window happens to be within the territory and the
bird sees its own reflection in that window, an attempt will be made to drive
out the apparent intruder. Since the reflection does not go away, the local
bird fights its image for one fruitless hour after another. Birds
have even fluttered at their image in the shiny hubcap of a car parked in the
territory. Sometimes the outside rear view mirror gets the birds attention. SOLVING
THE PROBLEM If a
bird fights its image, it will exhaust itself in this hopeless task. The
useless hours spent in fighting the reflection very often cause the nest to
fail. The nest may not be properly constructed or the bird will fail to keep
the eggs warm because it spent so much time fighting the intruder. To stop this activity, something must be installed to
frighten the bird away or somehow the reflection must be reduced. Frightening
the bird. It has been recommended that a silhouette of a hawk be
placed on the outside of the window. It is hoped that this will frighten the
bird and cause it to veer away from the "hawk" before it gets close
to the window. Some people say that it has no effect what so ever while
others think that it has decreased the number of hits on the window. I
suspect that any piece of cardboard or paper fastened to the outside of the
glass will break up the reflection enough to be helpful. As indicated above in
Section 1, there is a new method using feathers that you should try.
It was first described in Bird Watchers Digest a few years ago. It involves
the use of feathers dangling outside the window on one or more strands of
monofilament fishing line. The details were given above. Some people have tied the shafts of several feathers together loosely so that there is
a cluster of feathers together that stick out in all directions. Why does this frighten birds? The most likely suggestion
is that loose feathers or some blowing about suggest that a bird has been
killed by a predator and perhaps birds instinctively stay away from an area
where there are loose feathers and possible danger. Bill Thompson III, the editor of Bird Watchers Digest and
his wife Julie have tested this
method at their rural home in Ohio that has many reflecting windows. Now the
Bird Watchers Digest store on the web is selling these "Feather
Guards" ready made. Their unit
has a plastic suction cup on each end of the fishing line to hold the string of
feathers loosely in front of the glass. Check their web site at www.Featherguard.com. If you wish to order one, click on
"Order Now"( it works better than the"Buy Now"
button.) If you want to sell some
in your store, click on "Wholesale Information". Some Stores that specialize in items for attracting birds
already have them in stock. Ask
around. I hope that you will try this feathers idea and let me
know how it works. Reducing the ReflectionA white material placed against the glass on the inside
usually will reduce the reflection enough to stop the attacks. Avoid pulling
a dark colored drape across for this will enhance the reflection. Similarly,
a darkened room with a clear glass window makes the reflection more
pronounced. One of simplest things to do is to temporarily tape up
pieces of newspapers on the inside of the window. Another treatment is to
spread a coating of white window cleaner on the inside of the glass. This
could be in large blotches so that your own view out the window is not completely
obstructed. At the present time efforts are being made to manufacture
a window glass that will appear to be frosted when viewed from the outside
and yet appear transparent like normal glass from the inside. If nothing else works for either the "attacks"
against the window or to prevent high speed collisions, you may need to cover
the outside of the window with a thin netting which decreases the reflection,
without seriously interfering with the view out the window. . |
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