Population Size of the Wedge-tailed Shearwater Puffinus pacificus Population in Pisonia grandis Forest on Heron Island in 1992

Abstract

Repeated counts of Wedge-tailed Shearwater Puffinus pacificus burrows were made in two 30 × 30 m permanent plots in Pisonia grandis forest on Heron Island in 1978,1979 and 1992. The results support the population estimates of Hill & Barnes (1989) and their suggestion that the shearwater population almost doubled (to c. 16 000 pairs) between 1983 and 1985. However, due to the wide confidence limits on most estimates, a more gradual increase (of c. 3% per annum) cannot be ruled out. The 1992 population estimate was 16 503 ± 3427 pairs. Because shearwaters are supposedly faithful to nesting sites, the increase poses questions about inter-island movement and social organisation within colonies. It may also present problems for management of the Heron Island population.