The biggest problem turned out to be the lighting. The building has 28 spotlights on the roof, 2000 lights in the windows and green emergency lighting. The facade of the Post Tower was adjusted differently during the observation period: sometimes it shone constantly in one color, sometimes blue birds flew over the facade in an effort to claim fewer victims. The study shows that the less intensively the tower was illuminated, the fewer bird strikes and the fewer deaths there were.
Because any light that radiates upwards or sideways attracts birds, the study authors write. Migratory birds in particular are susceptible to this, as they orientate themselves towards natural light sources in order to fly south in autumn. “The animals are disoriented by unnatural lights, such as from buildings, and fly in the direction of the light sources,” agrees Catherine Schlueter, consultant for bird protection at the German Nature Conservation Union (NABU). As a result, they get into the danger zone near tall buildings and collide with the window panes. Even small amounts of light are enough to attract birds. During the observation period, the blinds were regularly not fully closed, allowing the green light from the emergency lighting to shine through.