Official websites use. Share sensitive information only on official, secure websites. Email: m. Data on nestling development and body mass were analysed in a gradient of urbanization set in Warsaw, Poland, in two passerine species: great tits Parus major and blue tits Cyanistes caeruleus. Increasing levels of impervious surface area ISA delayed the age of fastest growth in blue tits. Nestling body mass was also negatively affected by increasing ISA 5 and 10 days after hatching in great tits, and 10 and 15 days in blue tits, respectively.
High levels of ISA also increased nestling mortality 5 and 10 days after hatching in both species. An analysis of selection differentials performed for two levels of urbanization low and high ISA revealed a positive association between mass at day 2 and survival at fledging.
This study confirms the considerable negative impact of imperviousness—a proxy for urbanization level—on offspring development, body mass and survival, and highlights increased selection on avian mass at hatching in a high ISA environment.
Keywords: birds, body mass, growth rate, imperviousness, phenotypic divergence, selection, urbanization. Urbanization leads to drastic and widespread alterations to both biotic and abiotic components of the environment Grimm et al. Concomitantly, urban areas are expanding worldwide. At present, cities and towns cover c. Urbanization usually involves habitat fragmentation and contrasted anthropogenic land use.
The environmental structuring of cities thus unarguably differs from natural habitats. Thus, the urbanization process can lead to both divergent phenotypes and rapid evolutionary change at rates exceeding those normally observed in nature Alberti et al. Several studies emphasized important differences in the reproductive strategies adopted by rural and urban avian populations; thus, birds inhabiting cities often exhibit earlier laying dates, smaller clutches and reduced brood sizes compared to their rural counterparts Chamberlain et al.
