Occupation of burrows as a means of estimating the harvest of Short-tailed Shearwaters in Tasmania

Abstract

The harvest of Short-tailed Shearwater chicks during the 1977, 1978 and 1979 seasons was estimated by counting bur- rows along transects in colonies before and after the season. Analysis of results showed that only five transects, each 100 metres long, were required to estimate accurately the proportion of burrows occupied. During incubation in December the mean percentage of burrows occupied in the 1979 season was seventy-six per cent. Before the season opened in March, it declined to between thirty-five and sixty-five per cent each season. Counting in April after the season showed that, in the colony reserved for non-commercial or private use, over eighty per cent of the chicks originally present in March were taken but at the colony reserved for commercial purposes the mean crop over three seasons was thirty-five per cent. Short-tailed Shearwaters are in no danger from exploitation but some heavily harvested colonies could be.