Aspects of Drooping Sheoaks (Allocasuarina verticillata) that influence Glossy Black-Cockatoo (Calyptorhynchus lathami halmaturinus) foraging on Kangaroo Island
Tamra F. Chapman A B and David C. Paton AA Discipline of Environmental Biology, University of Adelaide, Adelaide, SA 5005, Australia.
B Corresponding author. Present address: Department of Conservation and Land Management, Locked Bag 104, Bentley Delivery Centre, Bentley, WA 6983, Australia. Email: tamrac@calm.wa.gov.au
Emu 106(2) 163-168 https://doi.org/10.1071/MU05021
Submitted: 3 May 2005 Accepted: 28 February 2006 Published: 19 May 2006
Abstract
Glossy Black-Cockatoos on Kangaroo Island, South Australia, rely primarily on the kernels contained in the seed-cones of the Drooping Sheoak (Allocasuarina verticillata) as their food source. This study expands on previous studies of Glossy Black-Cockatoos foraging on Kangaroo Island by examining selection of patches, trees, branches and cones. The Cockatoos appeared to maximise food intake per unit of foraging time by foraging in trees with higher seed-fill and kernel ratio. Although not conclusive, this study suggests breeding birds may be more selective of high seed-fill and kernel ratio than non-breeding birds. Within the canopy of the Sheoaks, the Cockatoos cropped cones from branches with high densities of cones present on them. The Cockatoos also showed a preference for foraging in large trees, which appears to reduce the number of movements they have to make between trees. This would both limit the energetic costs of foraging and limit exposure to predators.
Acknowledgments
This study was conducted as part of a Ph.D. project (Environmental Biology, University of Adelaide) and the Glossy Black-Cockatoo Recovery Program. It was supported by an Australian Postgraduate Research Award, with additional support from the Australian Research Council, the Wildlife Conservation Fund, the South Australian National Parks Foundation and the Save the Bush Fund. The methods for measuring cone- and seed-parameters were developed with Gabriel Crowley. Lynn Pedler and Stephen Garnett provided advice and logistical support in the field. The many people who assisted with field work are listed in Chapman (2005). James Bullock, Emma Crossfield, Anthony Freebairn, Olivia Mills, Sara Ormsby and Jane Ryan processed samples in the Environmental Biology Laboratory at the University of Adelaide. Gabriel Crowley reviewed and made significant improvements to earlier drafts of this paper. We used the laboratory facilities and administrative services of the Discipline of Environmental Biology at the University of Adelaide and at the Species and Communities Branch of the Department of Conservation and Land Management, Perth, to carry out this project.
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