Social organisation and foraging ecology of the cooperatively breeding Chestnut-crowned Babbler (Pomatostomus ruficeps)
Dean J. Portelli A , Holly Barclay B , Deborah J. F. Russell C , Simon C. Griffith D and Andrew F. Russell C D EA Department of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
B Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK.
C Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
D Centre for the Integrative Study of Animal Behaviour, Macquarie University, Sydney, NSW 2109, Australia.
E Corresponding author. Email: a.f.russell@sheffield.ac.uk
Emu 109(2) 153-162 https://doi.org/10.1071/MU08065
Submitted: 24 November 2008 Accepted: 4 April 2009 Published: 10 June 2009
Abstract
An individual’s fitness is assumed to be maximised through early dispersal and independent breeding. However, offspring across a diversity of taxonomic groups delay dispersal and remain with at least one of their parents after reaching sexual maturity. Delayed dispersal and resulting family living are expected to arise when constraints exist on independent reproduction and where offspring benefit by remaining philopatric. A first step to elucidating the nature of such constraints and benefits for a given species is to have an understanding of the social organisation and habitat preferences of a species. The present study examined the social organisation, foraging preferences and characteristics of preferred foraging areas during a breeding season in the cooperatively breeding Chestnut-crowned Babbler (Pomatostomus ruficeps). During the study, groups of Babblers bred plurally in breeding units of two to 13 adults that occupied non-exclusive home-ranges averaging 38 ha, with larger groups occupying larger ranges. Babblers spent most of the day foraging, mostly on the ground, and preferred to forage within drainage zones. The preference for such zones probably arose because they offered both greater vegetative cover from aerial predators and biomasses of potential prey. These findings lead to the prediction that the availability of drainage zones within a group’s range will influence offspring dispersal decisions in Chestnut-crowned Babblers at the site studied.
Additional keywords: benefits of philopatry, ecological constraints, home-range, plural breeding.
Acknowledgements
We are grateful to Dr David Croft and Zane Turner at Fowlers Gap for their invaluable support and logistical help during this study, and to the University of New South Wales for permitting the work to be carried out at their field station. Lucy Browning, Peter Cale, Kazu Eguchi, Richard Kingsford, Enrico Sorato and Sarah Taylor helped with the manuscript. This work was conducted with approval from the UNSW Animal Care and Ethics Committee (04–63A) and Australian Bird and Bat Banding Scheme (Project Number 422). D. J. Portelli, H. Barclay and D. J. F. Russell conducted components of this study in partial fulfilment of B.Sc. (Hons) degrees at the University of New South Wales (Australia), the University of Cambridge and the University of Sheffield (UK), respectively. A. F. Russell was funded by the Royal Society (UK), the Natural Environment Research Council (UK) and the Australian Research Council.
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