The conservation of large rainforest parrots : a study of the breeding biology of palm cockatoos, eclectus parrots and vulturina parrots

Abstract

In this thesis I outline the breeding biology and likely causes of threat to three species of large parrot found in the New Guinea rainforest: palm cockatoos (Probosciger aterrimus), Pesquet's parrots (Psittrichus fulgidus), and eclectus parrots (Eclectus roratus). All species are threatened by loss of habitat. Palm cockatoos and Pesquet's parrots are further threatened by being hunted for food and the thriving trade in the latters' feathers. Eclectus parrots are more abundant and less threatened from hunting, and provide a good comparison with the two former species. I first describe the traditional people, how they use the resources of their land (including the parrots), and how attempts are being made to integrate conservation with their economic development. By training 23 traditional land-owners as assistants, I was able to monitor the breeding efforts and reproductive success at 51 palm cockatoo, 71 eclectus parrot and 34 Pesquet's parrot nest trees over 28 months at my 2645 ha study site. Some retrospective information was also attained from local people who knew about nest trees prior to the study. Only palm cockatoos and Pesquet's parrots showed any overlap in the species of trees they used for nesting. The hollows used by each of the three parrot species differed significantly in every quantitative physical characteristic I measured. Palm cockatoo hollows tended to be in the skywards-facing end of a broken, dead trunk. Pesquet's parrots were the only species to entirely excavate their own hollows; they used the trunks of dead trees, but their hollows had entrances that opened sideways. Eclectus parrot hollows were in taller, live trees and had entrance sites and angles that were more varied than the other two species. The density of palm cockatoo nest trees averaged 0.06 nest trees/ha, but the annual density of active nests was only 0.008/ha. The density of eclectus parrot nest hollows averaged 0.07/ha, but the density of active hollows each year was 0.023/ha. Pesquet's parrots excavated new nests each year and the annual density of these was 0.017 nests/ha. Eclectus parrots tended to nest closer to human settlements than either palm cockatoos or Pesquet's parrots. Palm cockatoos and Pesquet's parrots bred seasonally, with eggs being laid between June and October. In contrast, eclectus parrots occupied their nests and bred all year. In any one year one-sixth of all potential palm cockatoo nest trees were actually used for breeding, whereas eclectus parrot nests were active more than once per year on average. Similar figures for Pesquet's parrots were not available. Palm cockatoos always laid one egg, Pesquet's parrots laid one or two eggs, and eclectus parrots usually laid two eggs. Eclectus parrots were the most successful at fledging young- 54% of all eggs laid (in 66% of broods) resulted in a fledgling. This compares to 40% in palm cockatoos and 17% (in 20% of broods) in Pesquet's parrots. Whereas most losses in palm cockatoos and eclectus parrots were due to predation, Pesquet's parrots lost chicks (of all ages) through stqrvation. Data on chick growth, feeding rates, and preferred food types are also presented. I conclude that the major life-history traits that render palm cockatoos rare and vulnerable are their low density of nest trees and infrequent breeding, whereas Pesquet's parrots appear to be most affected by low breeding success. In contrast, frequent breeding attempts, relatively high breeding success, and relative immunity to human disturbance make eclectus parrots less rare and vulnerable. I suggest several recommendations to ensure the persistence of the three parrot species in the CMWMA in the short-term, and directions for future research to help secure their survival in the longer-term. Show more