Metabolic ecology of cockatoos in the south-west of Western Australia

Abstract

This study examined the metabolic ecology of six cockatoo taxa endemic to the south-west of Western Australia. As the availability of food is one factor that may influence the abundance and distribution of these cockatoos, we document here their baseline energy requirements and feeding patterns. Evaporative waterloss was also measured as this may correlate with the aridity of the species’ environment.

Basal metabolic rate was significantly lower at 0.62 ± 0.13 mL O₂ g^–1 h^–1 for the inland red-tailed black cockatoo than 1.11 ± 0.16 mL O₂ g^–1 h^–1 for the forest red-tailed black cockatoo, but there was no significant difference in metabolic rate between the two white-tailed black cockatoos (0.86 ± 0.18 for Carnaby’s and 0.81 ± 0.11 mL O₂ g^–1 h^–1 for Baudin’s) or the two corellas (0.95 ± 0.12 for Butler’s and 0.70 ± 0.04 mL O₂ g^–1 h^–1 for Muir’s). There were no significant differences between the two white-tailed black cockatoos, and between the two corellas, with respect to evaporative water loss. The inland red-tailed black cockatoo had a significantly lower rate of evaporative water loss (0.44 ± 0.07 mg g^–1 h^–1) than the forest red-tailed black cockatoo (0.70 ± 0.06 mg g^–1 h^–1), which is presumably an adaptation to its more arid habitat.

The total energy content of assorted native and introduced food items that form significant proportions of the diets for these cockatoos varied from only 0.17 kJ for a 9-mg Emex australis seed to 63.9 kJ for a 3-g Banksia attenuata nut. The energy content of each food item and the estimated daily energy requirements of the cockatoos enabled the calculation of the numbers of nuts/cones/seeds required by each species for a day, which ranged from 11 B. attenuata nuts for a Carnaby’s cockatoo to 3592 Persoonia longifolia seeds for a forest red-tailed black cockatoo.