A 15-ha plot of salmon gum woodland contained 241 hollows with an entrance diameter and depth exceeding 90 mm, in 173 trees, the majority (95%) in salmon gums. Occupancy of these hollows during the spring of 1978 was 47%; eight species of bird (six Psittaciformes, one Anseriformes and one Falconiformes) were involved. Galahs, corellas, red-tailed black cockatoos and Port Lincoln parrots were the most numerous hollow-nesting birds in the area; there were differences in the sizes of hollows they used, which were separable on entrance size and on inside diameter of the hollow 0.5 m below the entrance. There was a trend for hollow size to decrease in the order: red-tailed black cockatoos, corellas, galahs and Port Lincoln parrots. Red-tailed black cockatoos nested in more dead trees, or trees which were lower and had smaller canopies, than did the other three species. The woodland contained few young trees, trees were dying rapidly and there was no regeneration. This situation is typical for woodland throughout the agricultural area, and future prospects are discussed.

Food eaten by the short-billed form of the white-tailed black cockatoo, Calyptorhynchus funereus latirostris, was studied in 2 areas in which it breeds; Coomallo Creek, an area with large tracts of uncleared land and Manmanning, an area of extensive clearing with little native vegetation remaining. In both areas the birds relied on native vegetation, particularly the seeds of the Proteaceae, for food. Coomallo Creek appeared to have an adequate food supply whereas Manmanning, with little remaining native vegetation did not. During the non-breeding season, birds from Coomallo Creek wandered locally within 50 km of the breeding area, feeding on native vegetation, relying on seeds of the marri, Eucalyptus calophylla, and the Proteaceae. Birds from Manmanning migrate to the coast where they feed on seeds of the Proteaceae, marri and Pinus spp. which grow in large plantations on the coastal plain.

The short-billed form of the white-tailed black cockatoo has been studied at Coomallo Creek for 16 years (1969-84), during which time the distribution of natlve vegetation in the district has greatly changed, and its total percentage has diminished from 67% in 1969 to 34% in 1982. At the same time the breeding population of black cockatoos in the area has fallen by one-third (to about 40 breeding pairs), but without any decrease in nesting success or in nestling 'fitness' as measured by comparing nestling weights with those of earlier years. The results of this study have been used to derwe a technique to assess the viability of populations of the white-tailed black cockatoo in other areas. This may be done by finding several nests, weighing each nestling, and measuring the length of its folded left wing, then aging it from a curve for growth of folded left wing drawn up from known-age nestlings. The weights of the nestlings are plotted against the appropriate ages, based on data from Coomallo Creek. Areas where nestlings show decreased 'fitness', as established by this method, may be in the process of losing their populations of the white-tailed black cockatoo.

Data on nest hollows were collected from four study areas throughout the range of the short-billed form of the white-tailed black cockatoo, Calyptorhynchus baudinii latirostris, in south Western Australia. Hollows in trees are formed as a result of some destructive agent such as termites or fungi attacking the heartwood of the tree and breaking down the structure of the wood cells. The breaking off of part of the tree provides access to the hollow from the outside, and allows it to be used as a nest site. Throughout their breeding range, white-tailed black cockatoos will nest in any species of eucalypt which has a hollow of suitable size. The aspects of the entrances of hollows are not randomly distributed among compass groups, but the birds' selection of hollows was random. The aspect, depth to the floor and height of the entrance from the ground do not affect the success or failure of the nesting attempt. Female white-tailed black cockatoos searching for and preparing nest hollows chase female conspecifics from an area around their prospective nest tree. They continue this activity until they are incubating; this may result in suitable hollows not being accessible to other females. The rate of loss of hollows was 4.8 and 2.2% at two of the study areas. Hollows are being destroyed by all causes, particularly clearing for agriculture, faster than they are being created. Guidelines for the management of woodland must be drawn up so as to maintain a continuing supply of mature trees and protect hole-nesting species.

This paper describes the 15 different types of vocalization produced by the short-billed form of the white-tailed black cockatoo. The majority of calls appear to be related to group maintenance and co-ordination. The paucity of vocalizations used in sexual situations is probably related to the fact that the birds are long-lived, with pair bonds which are maintained throughout the life ofone ofthe partners. Analyses of one of the types of calls showed that it is possible to identify individuals from their calls and that this may be achieved by discrimination of the lengths of parts of the call. The importance of being able to identify individuals from their calls is discussed.