Non-adaptive adoptions of nestlings in the colonial lesser kestrel: proximate causes and fitness consequences |
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Authors: | José L Tella Manuela G Forero José A Donázar Juan J Negro Fernando Hiraldo |
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Institution: | Estación Biológica de Do?ana (CSIC), Avda Ma Luisa s.n., E-41013 Sevilla, Spain Fax: 34 95 4621125; e-mail: Tella@cica.es, ES
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Abstract: | We examined the causes, costs and benefits of adoption in the altricial lesser kestrel Falco naumanni. Specifically, we tested the intergenerational conflict hypothesis, proposed to explain adoption in some birds. Adoptions
involved 76% of the nests and 51% of the nestlings at a mean age of 25 days (12 days before fledging). Nest-switching nestlings
were not in poorer body condition, more parasitized or younger than their siblings, and body condition and prey delivery rates
of their parents did not differ from those of other parents. In the foster nest, adopted nestlings did not benefit from higher
feeding rates or a prolongation of the nestling period. They did not have fewer nest-mates or achieve higher rank within the
new brood. Thus, adopted nestlings did not improve their body condition and survival. Adult lesser kestrels seemed unable
to finely discriminate beween their own and alien chicks. Foster parents bore the cost of an increase of prey delivery rates,
although it did not affect their survival or subsequent reproductive performance. Therefore, our results do not support the
intergenerational conflict hypothesis, and suggest that adoption in this species is non-adaptive. Traditionally, the lesser
kestrel bred in cliffs where movement among nest-sites was restricted. Nowadays, about half of the colonies are in tiled roofs
which facilitate nest-switching by nestlings. The high rate of adoptions may thus be explained as reproductive errors associated
with the recent occupation of a new breeding habitat.
Received: 3 May 1996 / Accepted after revision: 19 January 1997 |
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Keywords: | Adoptions Intergenerational conflict Falco naumanni Offspring recognition Parental care |
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