Decline of Sooty Shearwaters, Puffin us griseus, on The Snares, New Zealand

Abstract

The number of Sooty Shearwater, Puffinus griseus, burrow entrances on North East Island of The Snares, New Zealand, declined from 3288000 (95% CI = 3.1-3.5 million) entrances between 1969 and 1971, to 2 061000 (95% CI = 1.9-2.2 million) between 1996 and 2001. This represents a decline of 37% over 27 years, or 1.72% per year (95% CI = 1.35%-2.12%). It is not known whether burrow occupancy has also declined. Possible reasons for decline include fisheries bycatch, climate change, and losses on other islands to predation by introduced mammals and harvest of chicks (muttonbirding). Reliable population estimates of other Sooty Shearwater populations will be important for establishing baseline estimates against which future population trends can be evaluated. If the decline in burrow numbers represents a similar decline in Sooty Shearwater numbers on The Snares and elsewhere, the decline reported here is substantial and enough to warrant listing of the Sooty Shearwater as a "vulnerable" species, according to criterion A3 designated by the International Union for Conservaion of Nature and Natural Resources (IUCN) in 2001.