Distribution and Abundance of Seabirds Off Phillip Island and Within Port Phillip Bay, Victoria, 1986-1988

Abstract

Seabirds were counted along standard transect routes off Phillip Island and within Port Phillip Bay, Victoria. During these surveys 37 taxa were recognised, although only 10-11 were regularly seen. Of 25 taxa recorded within Port Phillip Bay, 16 were also included in the 28 seen off Phillip Island. Differences between sites related mainly to the occurrence of albatross species off the coast, and the variety of terns seen within Port Phillip. Off Phillip Island, most records were of Short-tailed Shearwater Puffinus tenuirostris which dominated the estimated biomass; in Port Phillip Bay the Silver Gull Larus novaehollandiae was numerically more important though the Australasian Gannet Morus serrator contributed more to the biomass. In general, areas off Phillip Island supported a higher average density and biomass than did those in Port Phillip Bay, primarily due to the seasonal influx of shearwaters during breeding periods. Commoner species, apart from cormorants and shags, were seen to the southem-most ends of transects run off Phillip Island. Main feeding methods are considered and it appears that the species occurring off Phillip Island are essentially polyvorous, taking a range of prey species, whilst most in Port Phillip are piscivorous.