Nest defence against conspecific intruders in the Common Pochard Aythya ferina: natural observations and an experimental test
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.
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Document Type: Research Article
Publication date: December 1, 2009