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A bird flies into a window at top speed and drops to the ground. Another bird flutters against a window, tapping its beak against the glass as if knocking at a door. Why do birds attempt to travel through glass? Humans laugh or even try to prevent it from happening, but birds don't seem to understand. Thousands are killed each year during migration and nesting.
Bird Brains
In the case of a bird, "bird brain" doesn't mean stupid, it just means that they process things differently than you or I do. There are different reasons why birds might fly into glass. Let's explore a few.
- Migration – Migrating birds often travel quickly. When the reflection from a window (or group of windows) looks like trees or foliage, it's easy for a bird to be confused and to continue right into the glass. According to National Wildlife Magazine, 2,000 birds per year could be killed during migration by tall buildings in Chicago alone.
- Territorial Behavior – A bird's nesting site and surrounding area are its "territory". Like many other animals, a bird will aggressively protect its territory or food source, especially during breeding season. Songs, flying patterns, and dive bombing are methods of protection. Reflections, such as those on metal or glass, may be interpreted by a bird as a rival – and therefore "attacked".
Species That "Attack" Glass
There are several types of species that tend to think of glass as a threat. Some birds from the Northeastern U.S. include the American Robin, Northern Cardinal, Northern Mockingbird, American Goldfinch Wild Turkey, and Ruffled Grouse.
A pair of Northern Cardinals is nesting in the trees outside my window at work. I've seen them quite often, or at least I did earlier in the spring. In the morning, the female would often sidestep along the ledge of my window and tap at the glass. Until I researched this topic I thought she was trying to get into the office for nesting material!
What to Do?
Here are a few ideas to help prevent birds from either crashing into glass or repeatedly attacking glass. They are not foolproof, but could help.
- Use outdoor screens on windows
- Keep shades drawn during peak feeding hours to cut down on reflection
- Use window decals (experts say this is ineffective)
- Cover windows with strips of ribbon or netting
- Move bird feeders away from windows
- Don't wash your windows
There are new types of glass that can help ward off birds. Called "fritted" glass, small circles are etched into the glass and make it more visible. The etching doesn't make a visual difference to human eyes from a distance, but helps oncoming birds.
Resources:
http://www.massaudubon.org/Nature_Connection/wildlife/index.php?subject=Birds:%20Behavior&id=17
http://www.npr.org/templates/story/story.php?storyId=5076012
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Re: Smack! Why Do Birds Fly Into Glass?
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