FIRST RECORD OF COOPERATIVE BREEDING IN A THRYOTHORUS WREN

Publisher Website
Google Scholar
Abstract
Although offspring delay dispersal past the age of independence in many Thryothorus species, cooperative breeding has not been recorded in this genus. Here, I present the first observation of cooperative breeding in a Thryothorus wren (Buff-breasted Wren, T. leucotis). Of 41 offspring that delayed dispersal past the age of independence, 4 individuals stayed on their natal territory until their parent's next breeding attempt, indicating a low potential for cooperative breeding. Of these four individuals, one male provisioned 11- to 15- day-old nestlings and one female approached her parents' nest but was repeatedly driven away from it by her father. The retained female was apparently tolerated when in the vicinity of fledglings, but feeding was never positively confirmed. Received 10 May 2004, accepted 15 October 2004. In cooperatively breeding birds, more than two adults participate in a single breeding event, either by defending the nest, incubating eggs, or provisioning young (Brown 1987). This is the predominant social system in 18.5% of oscine passerine species with bipa- rental care (383 of 2,067 species), and occurs occasionally in another 3.7% of oscines clas- sified as pair breeders (Cockburn 2003). How- ever, patterns of nestling care are unknown for most passerines (n 5 2,385), particularly those in the Neotropics (Cockburn 2003); thus, cooperative breeding may occur in still other species. Intensive studies of populations of banded birds are needed to determine the extent of pair versus cooperative breeding in these species. Cooperative breeding may arise in several different ways, including when (1) indepen- dent offspring remain on natal territories until their parents' next breeding period (Cockburn 1998), (2) individuals initially disperse and then preferentially immigrate into social groups composed of related individuals (Bag- lione et al. 2003), and (3) groups of unrelated individuals reproduce together (Davies 1992). In the first case, delayed dispersal by offspring is a necessary prerequisite for cooperation. However, in some species in which offspring remain on their natal territories for extended periods, helping never occurs (reviewed in Ekman et al. 2001). Delayed dispersal by off-

This publication has 1 reference indexed in Scilit: