By Don MacGillivray
In the daytime, birds will often see the sky or nearby habitat mirrored in the windows of large buildings and believe there is a clear flight path instead of the deadly solid glass.
Likewise when migrating birds fly at night, artificial lighting in tall buildings confuse them and can cause them to either crash into the structures or to circle repeatedly until exhaustion brings them down. These lighted buildings are especially lethal in fog and rain when visibility is greatly impaired.
Birds are known to attack their reflection in windows during matting season when they need to defend their territories from perceived rivals. Their battles with their own reflection may be exhausting, but they usually don’t result in fatalities unless these birds die later, from internal bleeding, bruising or from predatory animals.
An example of these circumstances is the recently built Columbia Building in North Portland that is home to the Portland Bureau of Environmental Services.
An expensive, controversial project that is a showcase of sustainability which meets the highly regarded LEED Gold building standard, in spite of its celebrated design, during the fall and winter of 2013/14 twenty-seven birds flew into the building’s large plate glass windows with eight confirmed deaths.
Portland metro area is a heavily-used flight pattern for many species of migratory birds. This building in North Portland lies in the Pacific Flyway where many birds pass on their way to their summer and winter homes.
Nearby is a large park-like setting adjacent to the Columbia Slough with large trees and a pond that attracts many birds. The birds do not see building windows as obstacles. They believe the reflections are a continuation of the surrounding environment and when they hit the windows at great speed, they can be easily injured or die as a result.
It is ironic that a Great Blue Heron (on the bureau’s official logo) has been found pecking at their reflection in the glass.
Approximately half a billion birds die annually from window strikes in the United States according to recent studies. This is only exceeded by over a billion birds killed annually by both domestic and wild predators.
Probably more birds are killed as result of the changing or lost habitat that they depend on during their long annual journeys across the world.
Bird mortality from window strikes has been recorded in more than half the bird species in the United States. Over 200 species of birds migrate through Oregon, and many of them are small night-flying songbirds.
Here in Portland, the following list of birds are known casualties of window strikes: Flickers, Chickadees, Hummingbirds, Hawks, Kinglets, Nuthatches, Thrushes, Warblers, Tanagers and Sparrows.
Some of these are threatened species whose populations are already in danger of great loss or extinction.
There are many ways to potentially improve the safety of windows from errant birds. The large picture windows in homes are usually the worst culprits, but it is infrequent that residential windows become a problem needing attention.
If you have a need to make your windows free from bird strikes here are a few of the many possible suggestions.
Cover the outside windows by stretching agricultural netting taut across your problem windows at least three inches from the glass. A small mesh netting of one half inch or one inch is best so that birds can bounce off unharmed. The netting may be mounted on a frame similar to a storm-window for easy installation and removal. This is a widely used solution that is almost 100 percent effective.
A few simple alterations inside can make a difference too: keeping shades, curtains and vertical window blinds at least halfway closed. At night keep the interior lights turned off especially during spring and fall bird migrations.
If you find a bird dazed from a collision, examine it for external injuries. If the wings are uninjured and the eyes seem normal it will probably recover on its own. If the bird has a noticeable injury, seek professional care as quickly as possible.
Otherwise place it in a ventilated paper bag or cardboard box that is securely closed and leave it outside. It should be in a dark place, away from activity, not too warm, and out of reach of pets. Do not try to give it food or water, and resist handling it. The darkness will calm the bird while it revives, unless it is seriously injured.
If the bird doesn’t recover within one to three hours, but is still breathing, contact a wildlife rehabilitation specialist such as the Portland Audubon Society Center for Emergency Wildlife Care.
Any window in a building or home can prove deadly to avian friends and window strikes should be anticipated when residential and office buildings are designed. Ultraviolet reflective glass, such as Ornilux, is visible to birds and transparent to humans and there are also types of tinted glass or similar products that are satisfactory.
In October of 2013, Portland City Council adopted a resolution of policy guidelines that “encourage the exploration and use of bird-friendly designs and practices in city plans and policies.”
It was jointly lead by City Commissioner Dan Saltzman and the Audubon Society of Portland. The guidelines are voluntary, but the city will use them and encourage their use by private developers.
Other North American cities such as Chicago, New York, Toronto, and San Francisco began these preventive measures. Portland’s Bird Design Prevention Guide is an adaptation of the American Bird Conservancy’s 2011 template guide.
As cities and populations grow by becoming more attractive and complex, the greater the potential danger of our improved urban and natural areas are to being hazardous to the traditional bird habitats and migratory pathways for our feathered friends.