While there are increasing examples of phenotypic and genotypic differences between urban and non-urban populations of plants and animals, few studies identified the mechanisms explaining those dissimilarities. The characterization of the urban landscape, which can only be achieved by measuring variability in relevant environmental factors within and between cities, is a keystone prerequisite to understand the effects of urbanization on wildlife. Here, we measured variation in bird exposure to metal pollution within 8 replicated urbanization gradients and within 2 flagship bird species in urban evolutionary ecology: the blue tit (Cyanistes caeruleus) and the great tit (Parus major). We report on a highly significant, positive linear relationship between the magnitude of urbanization—inferred as either tree cover, impervious surface cover, or an urbanization score computed from several environmental variables, and copper, zinc and lead concentrations in bird feathers. The reverse relationship was measured in the case of mercury, while cadmium and arsenic did not vary in response to the urbanization level. This result, replicated across multiple cities and two passerine species, strongly suggests that copper, zinc, lead and mercury pollution is likely to trigger the emergence of parallel responses at the phenotypic and/or genotypic level between urban environments worldwide.

No abstract

Research on the occurrence and community composition of vector-transmitted protozoan haemoparasites in birds is heavily skewed toward passerines with many other orders underrepresented. In caprimulgids, a family of primarily ground-nesting, crepuscular/nocturnal birds occupying a wide range of dry habitats, research on protozoan haemoparasites is limited and in most cases based on only a few individuals. Here, using the molecular approach, the occurrence and diversity of parasites from four genera (Haemosporida: Haemoproteus, Plasmodium, Leucocytozoon; Trypanosomatida: Trypanosoma) were investigated in a representative of the family—the Eurasian Nightjar (Caprimulgus europaeus). Birds were sampled at a breeding location in south-eastern Poland at the beginning of the breeding season. Overall, 20 individuals, including 17 males and 3 females, were screened. Only 10% of birds were infected and in total, two parasite lineages—both representing Plasmodium genus—were identified. Detected parasite lineages were previously registered in a wide range of avian hosts. Known transmission areas of these lineages indicate that breeding populations of Eurasian Nightjars from south-eastern Poland contract infections on non-breeding grounds. This study reinforces earlier observations of the low prevalence of haemosporidians and trypanosomes in caprimulgids.

While there are increasing examples of phenotypic and genotypic differences between urban and non-urban populations of plants and animals, few studies identified the mechanisms explaining those dissimilarities. The characterization of the urban landscape, which can only be achieved by measuring variability in relevant environmental factors within and between cities, is a keystone prerequisite to understand the effects of urbanization on wildlife. Here, we measured variation in bird exposure to metal pollution within 8 replicated urbanization gradients and within 2 flagship bird species in urban evolutionary ecology: the blue tit (Cyanistes caeruleus) and the great tit (Parus major). We report on a highly significant, positive linear relationship between the magnitude of urbanization – inferred as either tree cover, impervious surface cover, or an urbanization score computed from several environmental variables, and copper, zinc and lead concentrations in bird feathers. The reverse relationship was measured in the case of Hg while Cd and As did not vary in response to the urbanization level. This result, replicated across multiple cities and two passerine species, strongly suggests that urban metal pollution is likely to trigger the emergence of parallel responses at the phenotypic and/or genotypic level between urban environments worldwide.