A behavioural ecology approach to traffic accidents: Interspecific variation in casuses of traffic casualties among birds

Birds and other animals are frequently killed by cars, causing the death of many million individuals per year. Why some species are killed more often than others has never been investigated. In this work hypothesized that risk taking behaviour may affect the probability of certain kinds of individuals being killed disproportionately. Furthermore, behaviour of individuals on roads, abundance, habit preferences, breeding sociality, and health status may all potentially affect the risk of being killed on roads. We used information on the abundance of road kills and the abundance in the surrounding environment of 50 species of birds obtained during regular censuses in 2001-2006 in a rural site in Denmark to test these predictions. The frequency of road kills increased linearly with abundance while the proportion of individuals sitting on the road or flying low across the road only only explained little additional variation in frequency of road casualties. After having accounted for abundance, we found that species with a short flight distance and hence taking greater risks when approached by a potential cause of danger are killed by cars. These findings suggest that a range of different factors indicative of risk-taking behaviour, visual acuity and health status cause certain bird species to be susceptible to casualties due to cars