Survival of adult and nestling western lon-billed corellas, Cacatua pastinator, and Major Mitchell cockatoos, C. leadbeateri, in the wheatbelt of western Australia

Abstract

The western long-billed corella, Cacatua pastinator, and the Major Mitchell cockatoo, C. leadbeateri, were studied in the central wheatbelt of Western Australia from 1977 to 1983. Nestling and breeding adult birds were individually marked with patagial tags and their survival was calculated from resighting of tagged birds. Mean annual survival of adult male and female western long-billed corellas and Major Mitchell cockatoos were 94.2%, 93.2%, 92.9% and 81.3%, respectively. Survival of immature birds was less than that of adults and only 9% of male and 23% of female western long-billed corellas survived to age of first breeding at three and five years, respectively; 20% of male and 31% of female Major Mitchell cockatoos survived to age of first breeding at two and three years, respectively. The use of patagial tags had no significant effect on the survival of adult birds; the situation with immature birds is less certain, but the data suggest that any effect was small. Dispersal had only a slight negative effect on 'survival' of immature Major Mitchell cockatoos. The lower survival of immature birds was attributed to increased predation while in the locally nomadic immature flocks. Data on survival and productivity suggest that the populations should be stable or slowly increasing and this is in agreement with the data on the populations.