Seasonal movements and habitats of the silver gull, Larus novaehollandiae Stephens, in south-eastern Australia.

Abstract

During 1953-63, 53,026 young and 1191 adult silver gulls, Larus novaehollandiae Stephens, have been banded at 52 localities throughout south-eastern Australia. Analysis of the 1310 significant recoveries and 190 band numbers resighted shows partial migration, especially by younger birds, between breeding colonies and winter refuge areas. Dispersal from colonies varies widely in proportion of birds involved, presumably according to the winter food resources of the breeding area, and in direction and distance, which are determined by the location of survival areas. There is no geographical cline. Constancy of return by young and breeding adults to their own colony is high. The habitat requirements of the silver gull for survival and breeding are discussed, and the differences in dispersal patterns between colonies and regions are explained on the hypothesis that food supply during the non-breeding season is the critical factor. It is concluded that the potential breeding population exceeds the amount of suitable island sites available, despite considerable use of inland habitats and some sites of marginal quality.