This report is part of an ongoing long‐term study of the black petrel, Procellaria parkinsoni, on Great Barrier Island (Aotea Island) that was begun in the 1995/96 breeding season.
During the 2009/10 breeding season, 393 study burrows within the 35‐ha study area near Mount Hobson were checked and intensively monitored. Of these, 244 were used by breeding pairs, 99 by nonbreeding adults and the remaining 50 burrows were non‐occupied.
By 9 May 2010, 158 chicks were still present in the study burrows and 22 had already fledged, corresponding to a breeding success of 74%.
Nine census grids were monitored within the study area and accounted for 155 of the inspected burrows and 152 study burrows, with 88 burrows being used for breeding.
Fortyone chicks from earlier breeding seasons were recaptured within the Mount Hobson colony area this season (a total of 94 ‘returned chicks’ have been caught since the 1999/2000 season).
Twentysix random transects were surveyed in the study area and when compared with transects conducted in the 2004/05 season showed an apparent 22% decline over that period.
Modelling of the black petrel population on Great Barrier Island (Aotea Island) was updated and indicated the population trend may lie anywhere between ‐2.4% and +1.6% per annum, the certainty driven primarily by uncertainty over juvenile survival. Analysis of the census grid and transect data estimated the black petrel population from the 35‐ha area around Mount Hobson to be in the range of 2781 to 3287 birds.