Increased sedentariness in European blackbirds following urbanization: A consequence of local adaptation?

  • Partecke J
  • Gwinner E
  • 197

    Readers

    Mendeley users who have this article in their library.
  • 109

    Citations

    Citations of this article.

Abstract

Urbanization changes local environmental conditions and may lead to altered selection regimes for life history traits of organisms thriving in cities. Previous studies have reported changes in breeding phenology and even trends toward increased sedentariness in migratory bird species colonizing urban areas. However, does the change in migratory propensity simply represent a phenotypic adjustment to local urban environment, or is it genetically based and hence the result of local adaptation? To test this, we hand-raised European Blackbirds (Turdus merula) from urban and forest populations, quantified their nocturnal activity and fat deposition covering two complete migratory cycles and examined the consequences of a reduced migratory propensity for the timing of gonadal development (a physiological measure of the seasonal timing of reproduction). Although nocturnal activities differed strikingly between fall and spring seasons, with low activities during the fall and high activities during the spring seasons, our data confirm, even in birds kept from early life under common-garden conditions, a change toward reduced migratoriness in urban blackbirds. The first score of a principal component analysis including amount of nocturnal activity and fat deposition, defined as migratory disposition, was lower in urban than in forest males particularly during their first year, whereas females did not differ. The results suggest that the intrinsic but male-biased difference is genetically determined, although early developmental effects cannot be excluded. Moreover, individuals with low migratory disposition developed their gonads earlier, resulting in longer reproductive seasons. Since urban conditions facilitate earlier breeding, intrinsic shifts to sedentariness thus seem to be adaptive in urban habitats. These results corroborate the idea that urbanization has evolutionary consequences for life history traits such as migratory behavior.

Author-supplied keywords

  • Adaptation
  • Colonization
  • European blackbird
  • Life history
  • Microevolution
  • Migratory behavior
  • Partial migration
  • Phenotypic plasticity
  • Selection
  • Timing of reproduction
  • Turdus merula
  • Urbanization

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document

Authors

  • Jesko Partecke

  • Eberhard Gwinner

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free