Do roads select their prey A comparison of bird roadkill data with local availability

Road traffic collisions are an important mortality source in bird populations. While it is known that some species are more susceptible to road-killing than others, the underlying reasons remain largely unknown. We test the hypothesis that bird vulnerability to vehicle collisions is strongly influenced by morphological, ecological and behavioural traits, thus providing a general basis to predict the species potentially most at risk from road-killing. Bird roadkills were collected from daily surveys conducted during the breeding seasons of 2009-2011, along 50 km of roads, while bird abundances were estimated from point counts conducted around roads during the same periods. Selective mortality was tested in relation to species identity and several species traits. We detected 2,225 bird roadkills belonging to at least 73 species. Most birds showed roadkill rates proportional to their abundance. However, nine species were road-killed more (or less) often than expected from their abundances, with a strong positive selection found for Blue tit Parus caeruleus, Blackcap Sylvia atricapilla and Goldfinch Carduelis carduelis. We provide evidence that birds most vulnerable to road-killing seem to be small passerines that often forage in shrubs and small trees. Efforts should thus be directed towards reducing road-related mortality for this type of species, particularly where roads cross habitats occupied by species of conservation concern meeting these traits.

abundance; avian collisions; species traits; foraging; Manly's index; prey selection