Birds of many types have been killed by flying into glass windows and doors. In fact, according to the Audubon Society, recent evidence shows that collisions with glass may be a major source of avian mortality that's widely overlooked. Experts believe that over 100 million birds die each year in collisions with buildings and skyscrapers in the United States and Canada alone.
Although there are several variables which account for bird strikes, the primary cause is reflection. Birds become confused or startled and rush to to cover or open sky; unfortunately they often mistake a reflection for the real thing.
In cities the biggest kills typically occur at night during spring and fall migrations, when building lights appeared to lure birds into deadly collisions. Light-dimming campaigns, such as those led by the Toronto-based Fatal Light Awareness Program, have helped reduce the problem.
The best and most cost effective idea in helping birds avoid window collisions is the use of WindowAlert Decals. WindowAlert is a high-tech decal that may be applied to home and office windows. Each decal contains a component which brilliantly reflects ultraviolet sunlight. This ultraviolet light is invisible to humans, but glows for birds. WindowAlert decals help birds "see" windows and thus avoid striking the glass. Click Here for more information.
Facts About Bird Vision From WindowAlert
Birds enjoy sharper vision than humans. Birds can see certain light frequencies--including ultraviolet--that humans cannot see.
In fact, many songbirds have feathers that reflect ultraviolet light. This light is used to communicate species, gender, and perhaps even social standing. Birds can see this ultraviolet light under normal, daylight conditions. Humans require the assistance of a black light.
Why do birds see better than humans?
1) Both birds and humans have photoreceptive 'cones' in the retina located at the back of the eye. These cones allow us to see color light. The human eye contains 10,000 cones per square millimeter. Songbirds, for example, have up to 12 times this amount or 120,000 cones per square millimeter.
2) In humans, these photoreceptive cones consist of three types. Each cone is sensitive to red, green, or blue light. This is called trichromatic color vision. Birds have an extra cone for quadchromatic color vision. This extra cone expands the visible light spectrum, allowing birds to see ultraviolet frequencies.
3) During low-light conditions, both humans and birds rely on photoreceptive ‘cell rods’ in the retina. The human eye has 200,000 cell rods per square millimeter. Some birds, such as owls, have up to 1,000,000 cell rods per square millimeter.
4) Bird eyes, on average, account for 15% of the mass of the bird’s entire head. Human eyes, by contrast, account for less than 2% of the head.
5) Bird retinas, in contrast to humans, contain no blood vessels. This prevents light scattering and thus provides birds with greater visual acuity than humans.
Here are other ways to reduce bird strike occurences in homes and small buildings:
Bird strikes often follow a pattern - the same windows on a house or building may be repeatedly struck, while others are never struck. Observation and attention to bird attractions such as water, food and cover, will help identify the small percentage of glass area which causes the most problem.
• reduce window reflection
Put a screen or a shade cloth over the window which is nearest to bird activity. A shade cloth, available at hardware stores, is a plastic mesh that allows you to see through, yet keeps the windows from having reflections. If you have blinds, turn them so they are slightly closed, this will reduce reflection. White shears also work to reduce reflection while being able to see through.
This transparent film adheres to the exterior surface of a window, and allows ample light to pass through to the interior, while reducing the window's exterior reflectivity and transparency. Presently used for commercial and retail advertising on glass. The cost is approximately $4.00 US per square foot.
• place a hawk silhouette in your window
Most smaller birds will avoid the company of hawks, especially the sharp-shinned hawk which flies low into cover, often near feeders, and preys on small birds. A hawk simulation can be placed on your window or door to discourage birds from flying in this direction.
• tack up a temporary cover
Sometimes a more-aggressive behavior occurs, typically in the breeding season, where a bird repeatedly 'attacks' a window. Seeing its own refection as another bird, it's trying to drive it away, as songbirds are competitive during breeding times. A cloth, piece of netting or solid material can be placed on the outside of the window for a few days to break the bird of its habit. Or you can install indoor-outdoor blinds on the outside of the window.
• place sun ornament, crystal or other objects in your window
Sun ornaments, crystals, strips of cloth and other objects in the window will help birds know they can't fly through. Avoid hanging plants in front of the window - this can further confuse the bird who may fly towards the plant looking for shelter. Double-pane windows have enhanced reflection and are harder for a bird to see through; hanging objects would work better when placed outside the window. Stained Glass Suncatchers, Mini 3-Dimensional Windows, or Fly-Through Window Magnets work well for this purpose.
• locate bird feeders close to, or further away from windows
Feeders should be either further back in the yard or up close within 2 or 3 feet of the window. By placing the feeder up close, birds come in at a slower speed; they're less likely to get hurt during escape because window stikes occur at slower speed. By placing the feeder further out (10 feet or more), the bird has more room to manoevre. Window bird feeders do not encourage bird window strikes.
• block 'through-house' line of sight to the outdoors
Are any windows in your home oriented such that, from the outside, there is a clear view through the house and to another window looking to the outside? A bird may see this as a flight path. This can be changed simply by putting up a shade on the one window, or closing a door or similar obstruction which breaks the open view.
If you find a bird stunned by a window collision:
In many cases when a bird collides with a window, it is just stunned and will flying again within an hour, after they regain their senses. With gloved hands, carefully pick up the bird and place it in a safe area away from cats and other predators. In cool weather, place the bird in a well-ventilated box in a warm area to recover. Avoid handling the bird and the box as much as possible. Never handle birds or any other wild animal with your bare hands.