Breeding Ecology of the Western Long-billed Corella, Cacatua pastinator pastinator

Abstract

The breeding ecology of a small population of the western long-billed corella, Cacatua p. pastinator, was investigated for 6 years in the central wheatbelt of Western Australia. Pair-bonds tended to be long-lasting; however, the divorce rate for birds breeding for the first time was 25% with an overall rate of 15%. Females formed stable pair-bonds by age 2, and bred for the first time between 3 and 5 years old; males started breeding when 5 years old. Clutches (range from one to four, mode three) were started in early August; 78% are started in the last 3 weeks of the month. Mean clutch size, brood size and number fledged were 2.7 , 1.9 and 1.6 respectively; there were no significant differences in these parameters among the six years of the study. Hatching was asynchronous and was followed by the death of the young nestlings when they were significantly smaller (77%) than their older siblings. Nestlings fledged when they were about 60 days old; neither their mass or degree of wing growth influenced fledging age. Mean mass of fledglings from broods of three was significantly greater than that of broods of two or one. Productivity was assessed by the numbers of young fledging, surviving the post-fledging period, and reaching independence. Neither mass nor condition at fledging influenced any of these measures; productivity in all three increased with clutch size. Rainfall and temperature had no influence on the numbers fledged, but the number reaching independence was significantly and positively correlated with the mean maximum summer temperature. The results are discussed in relation to the results from studies of other species of cockatoos living in the wheatbelt of Western Australia.