Mortality and Dispersal of Juvenile Galahs, Cacatua roseicapilla, in the Western Australian Wheatbelt

Abstract

'From 265 tag or band returns (11% of the birds marked) shooting accounts for most galah deaths in the Western Australian wheatbelt, with cats, raptors and motor vehicles as other major mortality factors; a quarter of the young birds that leave the nest may die before they are deserted by their parents after 6 weeks. Newly independent galahs tend to disperse down-wind to the north-west from then on during the dry summer and autumn (January-April). In late autumn and winter dispersal becomes roughly random and the distance travelled increases. Of galahs marked as juveniles and later found dead, 80% had travelled less than 20 km, whilst one third had remained within 5 km of where they were hatched or netted. Juvenile dispersal appears to end in the second autumn of life, when individuals tend to join flocks of non-breeding birds that are only locally nomadic. It is from these local flocks that replacements to the resident breeding pool of adult birds come.