A sudden, dull thud against the window—a bird has flown into it, lies dazed on the ground, is seriously injured, or has not survived the impact. Often, bird casualties on glass panes or reflective surfaces go unnoticed because cats, martens, and other animals quickly find the injured birds, or because injured birds can still travel some distance, or because orphaned chicks or eggs die silently in their nests. The imprint of the feathers on the windows then disappears the next time the windows are cleaned.

The problem is that glass is transparent and often reflects the surroundings and nature. In both cases, birds cannot perceive this as an obstacle. With reflective panes, for example, birds see the mirrored sky, trees, or bushes and collide with the pane, which is invisible to them.

Particularly high sources of danger are buildings with large or largely contiguous window fronts, transparent situations, corner glazing, reflective facades, or interior lighting at night. Free-standing glass walls (wind, weather, or sound protection) should also be mentioned here.

In suburban areas, green residential areas, or glass near trees, increased bird flight is also to be expected, which can significantly increase the risk of bird strikes even with smaller window sizes.

The solution: windows can be made bird-friendly!

The simplest solution is to avoid using too much glass. However, where glass is necessary, frosted, colored, printed, or textured panes or visible films that can be applied retrospectively should be used. Permanently closed blinds, curtains, or similar design elements can also help, as long as they are closed. Light should always be used intelligently and, especially during bird migration periods, dimmed on and in buildings and switched off at night.

This is hardly noticeable to humans, but easily perceptible to birds!

The well-known sticker with the silhouette of a bird of prey has been proven not to work. It merely shows the places where there are problems with birds colliding with glass!

The decisive factors for the effectiveness of measures are always the distance, coverage, contrast, and external reflectivity of windows or reflective surfaces.