Nest site selection and breeding success in three Turdus thrush species coexisting in an urban environment
Abstract
The process of establishing breeding populations of birds in small towns of Central Europe provides a unique opportunity to study them during synurbization in statu nascendi. Over the years 2006-2011, we investigated the breeding ecology of three coexisting thrush species Turdus spp. in the urban habitats of the town of Bardejov (NE Slovakia).
We studied nest distribution, nest predation in relation to nest placement and the breeding success of the Common Blackbird T merula, Fieldfare T pilaris and Song Thrush T philomelos. The study species differed significantly in terms of microhabitat characteristics and vertical spatial distribution, expressed as the nest location height (Blackbird < Song Thrush < Fieldfare), the distance from the town centre (Fieldfare < Song Thrush < Blackbird), the distance from the nest tree to human paths and buildings (Blackbird < Song Thrush < Fieldfare) and the average distance between breeding conspecific pairs (Fieldfare < Blackbird < Song Thrush).
We also found significant differences in nesting microhabitats (conifers, deciduous trees and shrubs) usage (breeding in conifers: Song Thrush < Blackbird < Fieldfare). On the other hand, no significant differences were found in breeding success and predation between species.
A major factor affecting the predation rate was the distance between nests and the distance to human paths and buildings, and with Fieldfares and Common Blackbirds also the height of trees and the distance to the town centre. Our results suggest that ecological segregation among closely related species can also be common in a changed, urban environment.