The demography and cooperative breeding behaviour of the rufous treecreeper, Climacteris rufa

Abstract

I examined the demography and cooperative breeding behaviour of the rufous treecreeper, Climacteris rufa, in the south-west of Western Australia. Social organisation, breeding behaviour, reproductive success, survival and dispersal were measured over 3 years. The species lived in cooperatively breeding groups of 2–7 individuals, which occupied a territory year round. Most groups comprised a primary male and female (probably breeding) and offspring from previous breeding seasons (helpers). Territory defence was variable, particularly during the breeding season when individuals would feed nestlings in adjacent territories. The social organisation of the species was based on neighbourhoods of interacting territories. All group members provisioned nestlings, and the primary male and female significantly reduced their provisioning effort as the number of helpers increased. Total nest success for the 3 years was 78% and mean annual productivity was 2.1 (0.18). Fledgling and juvenile survival rates were relatively high (0.76 and 0.46 respectively), but adult survival rate (0.76) was comparable to that of other passerines of the temperate Southern Hemisphere. Dispersal of juveniles appeared to be female-biased. The demography of the rufous treecreeper was consistent with other old endemic Australian passerines. High adult survival resulted in few breeding vacancies for non-breeders and this is probably an important factor in the evolution of cooperative breeding in the species. Cooperative breeding also appears to be influenced by habitat saturation and a cost–benefit trade-off between remaining as a helper in high-quality territories and dispersing to poorer-quality territories where reproductive success may be low.