A population and harvest intensity estimate for Sooty Shearwater, Puflinus griseus, on Taukihepa (Big South Cape), New Zealand

Abstract

We estimated the total number of burrow entrances, chicks and total population size of the Sooty Shearwater, Puffinus colony on Taukihepa (Big South Cape), the largest of the 36 Titi Islands where Titi (Sooty Shcarwater chicks) arc harvested. Between 1999 and 2005 we surveyed six manu (family birded areas) as well as a colony in the interior forested region on the island, measuring entrance density and burrow occupancy and habitat variables, as well as recording birders' harvest intensity. We found little support for any relationship between habitat variables and entrance density on the surveyed manu. Therefore we used a detailed aerial image to map areas and extrapolate these estimates to island totals and a simple population model, incorporating known demographic parameters to calculate the total population size. We estimated that the island contains 1.67 million (95% CI: 1.47-1.88) burrow entrances and 1.12 million (0.959-1.28) breeding pairs, equating to a total of 5.31 million (95% CI: 3.98-6.77) juveniles, pre-breeders and adults associated with the island. Assuming the harvest intensity on the surveyed manu 0.18% (0.16-0.21) was similar elsewhere on the unsurveyed but harvested region of the island, we estimated that ofthe 807000 (712000-901 000) fledging chicks on the island, 137000 (105000-173000) are harvested each year. These findings highlight the importance of the island both in terms of total Sooty Shearwater population in New Zealand and to the Rakiura Maori who harvest the Titi.