Reproductive Parameters, Chick Growth and Adult 'Age' in Australasian Gannets Morus serrator Breeding in Port Phillip Bay, Victoria, in 1994-95

Abstract

Reproductive parameters of Australasian GannetsMorus serrator breeding at Pope’s Eye in Port Phillip Bay, Victoria, Australia were examined in the 1994—95 breeding period. Contents of individual nests were determined during routine visits, and eggs and chicks measured. Nests and breeding birds were assigned to groups based on position and adults of known age (previously banded as chicks) as indicators. A severe storm in November 1994 removed most nests and resulted in extensive re-laying, particularly by older (centrally nesting) birds. The ability to relay and successfully raise young suggested that food (preferentially Pilchards Sardinops sagax, although gannets take a wide range of fish at this location) was not limiting, being abundant even towards later stages of the breeding cycle. ‘Older’ adults formed more central nests, laid earlier, and replaced more lost eggs than younger birds. Chicks of older adults were produced earlier and were heavier at comparable ages than those of younger birds. Age influences some reproductive parameters, and hence lifetime reproductive success, in this species as it does in other seabirds.