Characteristics of Marri (Corymbia calophylla) fruits in relation to the foraging behaviour of the Forest Red-tailed Black Cockatoo (Calyptorhynchus banksii naso)

Abstract

Forest Red-tailed Black Cockatoos (Calyptorhynchus banksii naso) feed predominantly on seeds of the eucalypt Marri (Corymbia calophylla) and often only from specific feed trees. There was no difference between wet weight of fruits from feed (24.1 ± 1.72 g) and non-feed trees (23.2 ± 1.57 g), but trees from which Forest Red-tailed Black Cockatoos fed had a significantly higher seed number per fruit (3.9 ± 0.18), a greater individual dry seed weight (0.10 ± 0.003 g) and total seed weight per fruit (0.39 ± 0.02 g), and a higher ratio of total seed dry weight to fruit wet weight (0.02 ± 0.001) compared with non-feed trees (3.1 ± 0.20 seeds per fruit; 0.09 ± 0.005 g individual seed dry weight; 0.29 ± 0.020 g total seed dry weight per fruit; 0.013 ± 0.001 ratio of total seed dry weight to fruit wet weight). Discriminate analysis had a limited capacity to predict Marri use by Forest Red-tailed Black Cockatoos, correctly classifying about 70 % of feed trees. Seed number and total seed mass were the best fruit characteristics for the prediction of tree type. We conclude that Forest Red-tailed Black Cockatoos selectively forage from trees with fruits that have a high seed yield, but the method by which the cockatoos select these trees is unclear.