Survival and Seasonal Movements of the Cattle Egret in Eastern Australia

Abstract

Recoveries from 7849 Cattle Egrets Ardeola ibis coromandus banded as nestlings at eight heronries in southeast Queensland and north-east New South Wales over six nesting seasons were analysed six years after banding finished. The live recovery rate was 0.9070 and the dead and injured recovery rate, 0.88%. Birds with patagial tags apparently survived less well than colour banded birds and dispersed less far in winter. The oldest recovery of A. i. Coromandus is 11.1 years and mean life expectancy at fledging is 2.63 years and at one year of age it is 3.09 years, values similar to those of the nominate A. i. Ibis. The Cattle Egret is a partial migrant in eastern Australia. The pattern of its recoveries suggests a post-breeding migration predominantly south along the coastal plain, with the birds either becoming progressively more sedentary as they grow older and/or the more sedentary birds living longer than the long-distance migrants. Evidence for a general (although not invariable) philopatry comes from direct observation and a summer contraction of the recoveries towards the natal heronry, especially those of first year birds. The Cattle Egret's low first year mortality rate (40.6% in the present study) compared with certain other Ardeinae, seems to be a characteristic of populations of A. i. Coromandus and A. i. Ibis and may give impetus to the colonising process.