Life-history evolution and cooperative breeding in the sociable weaver

When compared to northern temperate counterparts, birds in the tropics and Southern Hemisphere regions, are characterised by low fecundity, long developmental periods and high Survival. This pattern has been attributed to hypotheses relating to food limitation, nest predation, and reduced seasonality leading to high adult survival. Still, to date few studies have investigated this issue. In particular, detailed studies from southern regions are scarce and as a result our understanding of this question remains weak. Another characteristic of 'southern' birds is a higher frequency of cooperatively-breeding species. It has previously been shown that cooperative breeding is most frequent amongst species with high survival and low fecundity. An explanation for this could be that long occupancy of territories by long-lived breeders leads to reduced opportunities of independent breeding by young birds. However, the biology of some species is such, that they do not experience shortage of breeding territories or other constraints, while still showing delayed dispersal and cooperative breeding. This study investigates what factors drive life-history evolution in a cooperatively breeding southern African passerine, the sociable weaver Philetairus socius. This species departs from the traditional cooperative breeding model in being a non-territorial colonial nester that inhabits an unpredictable semi-arid environment. Sociable weavers face no obvious constraints on independent reproduction, yet cooperative breeding is common. Therefore, I also aimed at determining what factors prompt delayed reproduction in this species, since this life history trait is the first step leading to cooperative breeding.

Grantor dc:publisher.institution

Percy FitzPatrick Institute of African Ornithology

Year dc:date.issued

2002

Author dc:creator

• Covas-Monteiro, Rita

Advisor dc:contributor.advisor

• Du Plessis, Morné

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/6944

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/6944