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Benefits of helping in a saturating environment: the Seychelles Warbler in Aride

Edelaar, P. (1995) Benefits of helping in a saturating environment: the Seychelles Warbler in Aride. Master's Thesis / Essay, Biology.

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Abstract

For the cooperatively breeding Seychelles Warbler (Acrocephalus sechellensis) , the decision to help is a trade-off between costs and benefits, which is influenced by the environment. The newly founded and increasing population of Seychelles Warblers on Aride Island, provides us with a prime example of a developing cooperative breeding system. Territories on Aride differ in quality (measured in terms of food availability), and warblers prefer territories of high quality for breeding. As higher quality habitat was being saturated by territorial warblers, helping behaviour started to occur on high quality territories because the fitness returns for delayed dispersal and helping were larger than for independent breeding. With an increase in groupsize, some birds established new territories in medium quality habitat. When medium habitat reached saturation, new helpers were found on territories of medium quality. As the population increased, average territory quality declined. Territories decreased in size and new territories became smaller and were situated in habitat of lower quality As a consequence, reproductive success of the warblers declined (lower breeding frequency and smaller brood size). Currently, breeding activity on Aride is synchronised with breeding activity on Cousin, on which breeding is determined by season, indicating seasonal effects on breeding on Aride as well.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Biology
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 07:47
Last Modified: 15 Feb 2018 07:47
URI: http://fse.studenttheses.ub.rug.nl/id/eprint/10020

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