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

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.