Aspects of Drooping Sheoaks (Allocasuarina verticillata) that influence Glossy Black-Cockatoo (Calyptorhynchus lathami halmaturinus) foraging on Kangaroo Island

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.