Thwap. Thwap. Thwap. Nothing says “springtime” like the maddening, irregular percussion of a bird's beak rapping repeatedly against your window. But why would any animal do this to itself (or to you, for that matter)?

It's not personal. We promise.

Each year, as the warm weather rolls around, migratory birds like robins (Turdus migratorius) and cardinals (Cardinalis cardinalis) stake out their territories in our neighborhoods. These nesting sites will be where they find mates and make babies, which means that location and security are of vital importance. A good mate-to-be will guard its territory against any unfamiliar bird face—even when that face is its own.

"What did you just say about my girlfriend?" Image credit: Dick Daniels via Wikimedia Commons // CC BY-SA 3.0

To you—safe, if irritated, inside your home—your windows appear transparent. But to belligerent birds in bright daylight, you may as well have tiled the exterior with mirrors. A robin looking at your house sees another robin looking back at him. And then, of course, they fight. (Turkeys attack clean, shiny cars for the same reason. No bird attacks a dirty car. We’re just throwing that out there. We’re here to help.)

Window attacks are different from bird strikes, the violent collisions that occur when a bird thinks your house is the sky and flies straight into it. Strikes are dangerous and often deadly for the birds involved. Territorial attacks are mostly just annoying for everyone, including the bird.

If you do hear a bird strike or your avian assailant attacks too hard for its own good, you may want to go outside and check that it’s okay. If the bird looks all right—both wings in place, eyes focused, able to sit upright—just leave it alone. It should be fine. If you can see some kind of injury, the best thing to do is to get the bird to safety. Use a clean towel to lift it into a dark container, like a shoebox, and set it down somewhere safe and quiet. After 15 minutes or so, try opening the box outdoors; the bird might fly out on its own. If it still shows no signs of recovery, take it to your nearest wildlife rehabilitation center.

If you tend to find your home beset by angry birds, there are some concrete things you can do. For starters, move any feeders away from windows to discourage visitors. Then stand outside on a bright afternoon and check your windows for glare. You can cover any offending surfaces with fine mesh netting or a drop cloth to disrupt the reflection, or apply one-way film to make the glass appear opaque from the outside. If you’re really desperate and have some time (and extra cash) on your hands, you can install shutters on the outside of the house.

Unfortunately, covering one window may simply push your problem a few feet away. American robins in particular have been known to attack as many as 15 windows in a single house. “A territorial bird can be very persistent,” the Massachusetts Audubon Society notes on its site. “The best course of action is to be patient and wait for the breeding season to end [usually around August].”

Hang in there.

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