Ever found a beautiful bird dead outside your home? Chances are it smashed into your window and never recovered. For every dead bird you find, just imagine how many were snatched up by a cat or pulled into the brush by some other critter. Worldwide, window collisions kill close to a billion(!) birds every year. With spring migration currently underway in the northern hemisphere, now is as good as ever to make your home bird safe.

It’s thought that birds hit windows because they see the landscape—trees, sky, clouds—reflected on the glass surface but do not realize that a hard, transparent surface lies between them and that apparent open space. Panicking birds, fleeing for cover to escape predators, are even more likely to fly into windows.

A related problem—more annoying than lethal—occurs when birds attack windows. It usually occurs in spring, and is due to birds’ urge to defend breeding territories. The male cardinal pecking at your window is fighting what he perceives as an intruding male—he doesn’t understand that it’s his own reflection. This territorial reaction may be so strong that the bird may exhaust himself, but it usually doesn’t result in fatal injury.

If you find a bird dazed from a window hit, place it in a dark container with a lid such as a shoebox, and leave it somewhere warm and quiet, out of reach of pets and other predators. If the weather is extremely cold, you may need to take it inside. Do not try to give it food and water, and resist handling it as much as possible. The darkness will calm the bird while it revives, which should occur within a few minutes, unless it is seriously injured. Release it outside as soon as it appears awake and alert. If the bird doesn’t recover in a couple of hours, you should take it to a veterinarian or wildlife rehabilitator. Remember that, technically, it is illegal to handle a migratory bird without a permit.