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Roadkill risk in European birds: The role of detection and plumage colouration

Morelli, Federico12; Benedetti, Yanina1

Published Jul 14, 2025 on Dryad. https://doi.org/10.5061/dryad.3r2280gv1

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Abstract

Wildlife-vehicle collisions (WVCs) are a significant cause of mortality among European birds. This poses a threat to the conservation of birds because pervasive human-related structures, such as road networks, are expected to expand over the continent in the next few decades. For this reason, a good understanding of the traits that make a bird species more vulnerable to being killed through a collision with a vehicle is essential. Traits such as body mass, plumage colouration, boldness, and behavioural characteristics can shape roadkill risks. Here, we first tested the presence of a phylogenetic signal in the roadkill rate of a pool of 55 European birds. Then, we explored the potential correlation between roadkill rate and several ecological characteristics of species. Overall, the incidence of casualties among bird species does not covary with phylogeny. Territoriality, body size, migratory strategy and diet were not significantly associated with roadkill rates in European birds. However, we found that more conspicuous birds and species characterised by a high percentage of dark brown colouration in their plumage were more affected by roadkill. The colour combinations brown dark with brown light and brown dark with grey dark seem less associated with higher roadkill rates. No correlation was found between roadkill rate and single-colour dominance (e.g., a high colour inequality) in European birds. Our findings suggest that a) species exhibiting more boldness and less shyness against humans (e.g., easier to be detected) are also species overall more active and consequently more likely to collide with vehicles on the roads, and b) some colours could play a role in the risk assessment of WVC for birds.