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The reproductive behaviour of brood parasitic birds has been of long-standing interest to evolutionary biologists, but some key features of this breeding tactic are largely unknown in particular species. Here we investigated antiparasitic tactics in ground nesting Common Pochard Aythya ferina females towards intraspecific brood parasitism. Using a conspecific female dummy we experimentally simulated a situation where a female returning to her own nest is confronted with a conspecific parasite. The behaviour of the tested females towards the experimental dummy was compared with their responses towards the stuffed female Ring-necked Pheasant Phasianus colchicus used as a control. The reactions towards both dummies were similar: Pochard females typically swam silently around their nests and observed the dummy. The lack of differences between the measured parameters recorded in the experiments with conspecific and pheasant dummies may indicate that female Pochards do not recognize the conspecific intruder as a specific threat. In addition, the responses of the incubating female towards the conspecific female on her nest were studied using continuous video recordings. The defence was not sufficient, since the intruders were never expelled from the nest. The only rejection technique recorded was that of the parasitic egg being removed from the nest with the aid of the bill. The data indicate that active sophisticated anti-parasitic tactics have not evolved in Pochards, although there is some level of defence towards intruding conspecific parasites.
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.
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