With the gradual increase in the use of glass in human buildings, and the expansion of human construction into bird migration corridors, the number of birds killed by glass impacts is steadily increasing. Glass strikes are the second most common cause of human-caused bird deaths, after habitat devastation.
Invisible Death
Birds crash into unsecured glass noise barriers, but also small glass surfaces on houses, apartment blocks, schools, office buildings, public transport stops, sheds, greenhouses, etc. Similarly, ordinary windows pose a deadly danger to birds if they are not supplemented with appropriate safety measures.
Birds are at risk in migration corridors, in towns and villages where they fly to feed or nest. A flying bird does not see an obstacle in a glazed area, but rather a reflective landscape. It, therefore, considers the surface as a space suitable for flight. This risk is further increased with the use of ‘mirrored’ glass.
How to Protect Birds
The lonely silhouette of a sticker of an owl or other predator will not scare or protect birds. It is not the shape of the sticker that matters, but enough stickers in any shape will help birds register the window as a dangerous obstacle. Similarly, a method based on the use of magnetic fields is ineffective in disrupting the geomagnetic orientation of birds.
Ornithological research shows that with the correct procedure, bird strikes on glass can be significantly reduced: even coverage of windows with patterns of any shape with gaps of 10 cm for vertical coverage and 5 cm for horizontal coverage is optimal. If the patterns are placed densely enough, they can be of any shape. The individual pattern should be at least 0,5 cm in size. It should contrast as much as possible in color with clear or reflective glass to make it as visible as possible to birds.
Due to poor or no measures, an incredible 100 million birds a year are killed in Europe by glass strikes. To put that into perspective, that’s 5 times more than birds hit by high voltage wires and 10 times more than the number caught by domestic cats.
Source: https://www.discovermagazine.com/planet-earth/billions-of-birds-die-annually-from-flying-into-windows-heres-why-and-how-to
