White-chinned petrel (Procellaria aequinoctialis) burrow density, occupancy, and population size at the Auckland Islands

In New Zealand's subantarctic Auckland Islands, the island-wide population size of white-chinned petrels (Procellaria aequinoctialis) is unknown. On ten islands in the group, surveys for burrow distribution were followed by whole-island burrow counts or stratified random sampling of white-chinned petrel habitat. White-chinned petrel burrow density, burrow occupancy, and slope-corrected surface areas were used to calculate the breeding population size. Burrows were patchily distributed and most abundant in dense megaherb communities. White-chinned petrel burrow density at Adams Island was 701 burrows/ha (95% CI: 480-803 burrows/ha). Burrow occupancy was 0.59 +/- 0.02 (mean +/- se) at the start of incubation. An estimated 28,300 (10,400-44,800) white-chinned petrel pairs breed on Adams Island. Including the small colonies on Ewing, Monumental, and Enderby Islands (together c. 100 pairs) and the estimated 155,500 breeding pairs on Disappointment Island, the Auckland Island group has an estimated 184,000 (95% CI: 136.000-237,000) pairs of breeding white-chinned petrels.