The Breeding Biology, Food, Social-Organization, Demography and Conservation of the Major Mitchell or Pink Cockatoo, Cacatua-Leadbeateri, on the Margin of the Western Australian Wheat-Belt

The breeding biology of the Major Mitchell or pink cockatoo, Cacatua leadbeateri, was studied over six years at Yandegin on the margin of the Western Australian wheatbelt. Neither winter nor annual rainfall influenced the timing of egg-laying, which was spread over August and September. Most clutches (n = 63) were of three or four eggs, 84% of which hatched; 64% of nestlings fledged successfully and, on average, 1.27 independent young per pair were added to the population each autumn. Breeding pairs remained together throughout the year, spending the non-breeding season in a Local Nomadic Flock of 30-50 individuals. Pairs usually renested in the same area each season, never closer than 1 km to another pair (mean nearest neighbour 2732 m). Hollows used by C. leadbeateri were characteristically shallow (< 1 m) and high up, whereas other cockatoos tend to be less selective. Such specific nest hollow requirements led to regular reuse of scarce traditional sites and consequent easy 'farming' of nestlings for the aviary trade; specificity also rendered the species more susceptible to loss of rare nest sites by clearing than were other cockatoos. Although C. leadbeateri are long-lived (adult c. 88% survival) and productivity at Yandegin appeared adequate to maintain a stable population, the shrinking distribution in the face of expanding wheat farming is irreversible. Conservation of the species depends on the protection of large areas of the remaining suitable semiarid woodland and the continuing strict enforcement of the complete ban on harvesting wild birds for the aviary trade.