Clutch Size and Productivity in 3 Sympatric Species of Cockatoo (Psittaciformes) in the Southwest of Western-Australia

Abstract

The galah, long-billed corella and red-tailed black cockatoo coexist throughout much of the northern wheatbelt of Western Australia. Various aspects of the breeding biology of these species were studied at Burakin and Three Springs in 1979. Laying began at the same time of year in all three, although the peak was later and the length of the laying period longer for the red-tailed black cockatoo. Data are given on clutch size, hatching success, nestling mortality, nestling period, fledging weight and productivity for each species at both study sites. The only significant differences between study areas were that the fledging weight and productivity of the galah were greater at Burakin than at Three Springs. Productivity was severely reduced in the galah by an unidentified nestling disease, and in the red-tailed black cockatoo by high infertility and nestling mortality of unknown cause. Between the species, incubation period and fledging period increased with body size but clutch size decreased with body size.