Graffiti saves birds: A year-round pattern of bird collisions with glass bus shelters

Abstract

The increase in the human population is bringing with it a concomitant rise in the number of novel man-made structures appearing in different environments, which may affect wildlife. Glass shelters at bus stops create surfaces invisible to many animals like birds and may increase their mortality; evidence for this is rare, however. The main aim of the study was to analyse the temporal variation and frequency of the risk of birds colliding with small, man-made, glass structures. A year-round survey investigating the frequency of bird collisions with 81 glass bus shelters was performed in south-western Poland. A total of 2467 visits to these bus stops yielded evidence of 155 collisions at 40 of them (mean: 1.9 per shelter, range 0–18). The bird carcasses most often found were of passerines, principally blackbirds Turdus merula. The traces left on the glass included feather remains (70%) and whole bird contours (30%). The probability of finding, during a single visit to a bus stop, that a bird had collided with the glass shelter tended to be higher in rural than in urban areas. Both dust and graffiti covering the glass panels of a bus shelter reduced the likelihood of collision. The occurrence of collisions was the highest in July-August and the lowest from November to February. Our study is the first in Europe and the first year-round study worldwide to demonstrate that such small man-made objects can cause death and injuries to birds. We suggest covering such shelters with non-transparent objects, e.g. city maps, paintings or other forms of artwork, in order to reduce the negative impact of these structures on local birds.