AVIS-IBIS

Birds of Indian Subcontinent

Experimental Evidence for Helping and Hindering by Previous Offspring in the Cooperative-Breeding Seychelles Warbler Acrocephalus sechellensis

Publication Type:Journal Article
Year of Publication:1994
Authors:Komdeur, J
Journal:Behavioral Ecology and Sociobiology
Volume:34
Issue:3
Date Published:1994
ISBN Number:03405443
Keywords:Acrocephalidae, Acrocephalus, Acrocephalus sechellensis
Abstract:Prebreeding Seychelles warblers (Acrocephalus sechellensis) frequently act as helpers on their natal territory, aiding in territory defence, predator mobbing, nest-building, incubation (only females) and feeding dependent young of their parents. In some cases helpers could attain breeding status (e.g. by joint-nesting) in their natal group and become co-breeders. Comparisons of group size and reproductive success on a given quality territory suggest that the presence of alloparents (helpers and co-breeders) significantly affects the reproductive success of their parents. The influence of alloparents on reproductive success was examined by removing alloparents from breeding units and comparing the success of natural-sized and artificially reduced groups. Removal experiments, controlled for territory quality, group size and breeder age, showed that the presence of one alloparent significantly improved the reproductive success of its parents. Analysis strongly suggests that this was entirely due to helping behaviour (i.e. providing care to offspring of their parents), thereby improving the helper's inclusive fitness benefits from staying at home. However, these experiments showed also that the presence of two or more alloparents in medium-quality territories significantly decreased reproductive success, compared with groups with one alloparent. Several lines of evidence suggest that this may have been due to the joint-nesting and reproductive competition that could occur in breeding groups, or simply to resource depression when a large number of previous offspring remained on their natal territory.
URL:http://www.jstor.org/stable/4600929
Short Title:Behavioral Ecology and Sociobiology
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