Prevent Window Collisions

Birds don’t recognize glass the way we do.

They see reflections of the sky and trees, which appear to them as a continuation of the sky. Birds are also drawn to vegetation inside, not realizing it’s behind glass—or they see a clear path through to the other side of a house when windows face each other.

Up to a billion birds are killed each year in window collisions. And it’s not just city buildings—homes are a major part of the problem.

Nearly 45% of window fatalities occur at houses.

Just because you haven’t seen a bird’s body doesn’t mean your windows are safe. Many birds fly away after impact but are gravely injured, later dying from blunt force trauma or predators taking advantage of their weakened state. Fractured bones, internal bleeding, and traumatic brain injuries are common.

City buildings do pose a serious risk as well, and collisions there are often catastrophic.

How You Can Help

If you’d like to make your home bird-safe, start by identifying problem windows. Large, plate-glass windows, or those that reflect vegetation, often see the most strikes. Even if only one bird has collided with a particular window, it’s likely that more birds are hitting it when you aren’t around.

Next, break up reflections:

Best option: External insect screens. They eliminate reflections and act as a cushion if birds do hit. They’re easy to install on existing windows, which is ideal.
If screens aren’t possible: Use tape, decals, paint, or special films to create visible patterns for birds.

Patterns should be at least ¼-inch in diameter and spaced no more than 2 inches apart. A 2" x 2" grid is especially important for protecting small birds, like hummingbirds. Dark patterns can be hard for birds to see when windows reflect dark colors, so medium or light colors often work best.

Other visual barriers: Hang paracords outside your windows, spaced about 4 inches apart. The paracord reflects on the glass, creating the illusion of 2" x 2" spacing.

Placement tips:

Avoid putting potted trees or large plants right next to windows, as they can create a false “flyway” through your home.
Use curtains, blinds, shades, awnings, or shutters to reduce reflections and light escaping through windows.

Turn off lights at night.

Birds collide with glass year-round, but most strikes happen during spring and fall migration. Since most birds migrate at night, artificial lights can attract them to buildings, increasing the risk of collisions or exhaustion.

Turn off unnecessary lights by hand or use timers and motion sensors.
If you work in an office building, encourage management to keep lights off at night during migration periods.

Reducing artificial light not only protects birds but also lowers energy costs and light pollution.

If a bird is injured by a window:

Never release it on your own. Even if it looks alert, it may have hidden injuries. Injured birds should always be taken to a licensed wildlife rehabilitator, who can provide the care they need to recover safely. Check the Resources page for wildlife rehabbers in your area.

Visit the American Bird Conservancy's website for more information on how you can prevent window collisions.