Cooperative breeding and density regulation in small island populations of the Seychelles warbler

Abstract

The faunas of tropical islands are particularly rich in endemic species, and constitute a disproportionately large proportion of the global biodiversity (Collar & Stuart 1985; Stattersfield & Capper 2000). In the last few centuries island faunas have become among the most threatened in the world, mainly because of anthropogenic effects such as human disturbance and the introduction of predators or competitor species (Stattersfield & Capper 2000). In contrast to species from temperate regions, we have little knowledge of the processes that regulate populations of tropical bird species, despite that fact that this knowledge is crucial to their conservation. In this thesis I studied population regulation in small isolated populations of the cooperatively breeding Seychelles warbler (Acrocephalus sechellensis). As this is a vulnerable species, direct manipulation of density through permanent removal of birds was not possible. However, translocations carried out as a part of a conservation project gave me the possibility to study density dependence of reproduction and survival in newly established populations. In addition I investigated the proximate mechanisms involved in helping behaviour and the long-term fitness consequences of group living.