Ornis Hungarica. vol.10. (2000) p.55-63.
Adoption of alien chicks in the Avocet: evolutionary aspects
Adoption of alien chicks has been reported in over 120 bird species. Adoption may influence the survival of both the adopted chick and the chicks as well as the behaviour and/or reproductive success of the adopting adult. This paper presents preliminary results on the formation and frequency of adoption and its potential costs or benefits in the Avocet (Recurvirostra avosetta). Fieldwork was conducted on alkaline lakes of the Kiskunság National Park, central Hungary, in 1998. I colour-ringed avocet chicks a few hours after hatching to make identification of individual broods possible. After the hatching of chicks their parents led them to feeding areas. Adoptions usually occurred during such brood movements. I observed adopted chicks in 13% of the resighted broods (n=30); one family adopted four alien chicks, whereas three other pairs adopted one chick each. Adopted chicks tended to live longer and fledge in higher proportions than their siblings that remained in their natal brood. Adopting adults spent less time giving alarm signals when predators approached than adults that had not adopted chicks. There was no difference in any other behaviour type between adopting and non-adopting adults. The chicks of adopting adults were more likely to fledge than chicks of non-adopting adults. These preliminary results indicate that adoption may be beneficial for both the adopting adult and the adopted young. This result can be applied in the practice of nature conservation in the artificial adoption or repatriation of chicks artificially hatched from nests that are threatened with destruction.