Hazards to Wild Birds Associated with Anthropogenic Structures and Human Activities—Results of a Long-Term Study in an Urbanised Area of the Alps

We analyse data from a rescue database collected at the Innsbruck Alpenzoo (Tyrol, Austria). The sample covers 33 years (1988–2020), and more than 5250 wild birds from 145 species originating from Innsbruck and the surrounding Inn Valley, one of the most densely populated areas in Europe. Both, the total number of birds as well as the number of bird species yearly admitted have increased since 1988. Orphaned nestlings and victims of glass collisions were the most common reasons for admission and responsible for the increase. Species’ susceptibility to accidental causes increased with regional abundance and degree of urbanisation. More urbanised species are characterised by a high proportion of nestlings and juveniles in the sample. The seasonal patterns of deliveries in these species show a peak in the late breeding season, and young birds are particularly susceptible to glass collisions and cat attacks. The species list also includes regionally rare wetland, upland and forest breeders and foreign migrants. Such species show a high proportion of admissions in autumn and collisions with windows play a greater role for short-distance migrants. Our data also suggest that small birds (<15 g body mass) are more likely to collide with glass panes than larger species. In conclusion, our data suggest that basically all bird groups and species are at least occasionally affected by human structures and activities in urbanised landscapes but support the notion that juveniles and migrants are more prone for accidents due to the lack of experience with anthropogenic structures in new areas.