The Influence of Synchronous Breeding, Natal Tree Position and Rainfall on Egret Nesting Success

Abstract

Factors commonly thought to influence the breeding success of colonial egrets were measured over 4 years. No significant difference in breeding success occurred between years, and the position of the natal tree in the colony did not affect breeding success. Evidence of synchronous breeding was found, but only intermediate Egrets had a higher fledging success for nests that fledged young during the peak nesting month. The amount of rainfall in the five months prior to the onset of nesting was positively correlated with the fledging success of Intermediate Egrets, suggesting the importance of food availability for this species. Nesting success found in New South Wales was compared to that reported elsewhere, and found to be less than that calculated to maintain stable populations. The problem of comparing fledging success between different studies with different criteria for determining is discussed.