Abstract

Summary: Glossy Black-Cockatoos on Kangaroo Island nest in large hollows in eucalypts, primarily Sugar Gums Eucalyptus cladocalyx, and usually near their principal food trees. A single egg is laid between late January and late July. Incubation is about 30 days and the nestling period 90 days. Nestling growth rate is slower than for other cockatoo species. Without protection most nests are likely to be pre-dated by Brushtail Possums Trichosurus vulpecula. With protection the probability of an egg resulting in a fledgling increases from 23% to 42%. However, competition from Little Corellas and Galahs, already occurring at a small proportion of nests, may become a significant threat in the future. Eggs laid before the end of March are more likely to succeed than those laid from April onwards. An equal sex ratio among nestlings contrasts with a ratio of about two males to each female among adults suggesting a greater mortality of females after fledging. Protection of nests against possums and management of competing cockatoos are recommended as measures required to secure the population on Kangaroo Island and to allow its return to mainland South Australia.