Apostlebird Struthidea cinerea
The Apostlebird is a co-operatively breeding bird which can live large groups of up to 17 birds. We were interested in examining the genetic and social make-up of these large groups. By examining patterns of relatedness and fine-scale genetic structure within Apostlebirds, we were able to determine what had previously been observed through behavioural observations: Apostlebirds do not disperse large distances, and natal philopatry is displayed by both sexes (although females may disperse over larger distances that males).
Given that Apostlebirds live in such large groups, we were interested to determine whether there was any variation in the contributions to incubation and nestling provisioning by individual members of the group. We found that contributions varied in relation to age, sex and breeding status. Young birds (<2 years) were less helpful than older birds, and spent less time incubating and feeding nestlings. Breeding females spent more time incubating than non-breeding females, although this pattern was not mirrored in males. We found individual provisioning rates were lower in larger groups, although the feeding rate per nestling increased.
To complete our study, we investigated the mating patterns of Apostlebirds, and found that the species adopts a flexible and context dependent mating strategies. Both monogamy and polygamy were detected, although most groups were monogamous. We also found that while there was a high level of relatedness within the group, the breeding pairs appeared to be less related than other potential pairings. We didn't find any conclusive evidence of extra-group paternity.
This research was conducted as part of a PhD carried out by Dr. Iain Woxwold, entitled “Social organisation, cooperative breeding and sex allocation in the apostlebird, Struthidea Cinerea “.
More information about this research can be found in these publications:
Woxvold, IA & Mulder, RA (2008). Mixed mating strategies in cooperatively breeding apostlebirds. Journal of Avian Biology 39: 50-56. Full text
Woxvold, IA, Adcock, GJ & Mulder, RA (2006). Fine-scale genetic structure and dispersal in cooperatively breeding apostlebirds. Molecular Ecology 15: 3139-3146. Full text
Woxvold, IA, Mulder, RA & Magrath, MJL (2006). Contributions to care vary with age, sex, breeding status and group size in the cooperatively breeding apostlebird. Animal Behaviour 72: 63-73. Full text
Photo: David Kleinert