A review of the distribution and size of gadfly petrel (Pterodroma spp.) colonies throughout New Zealand

Tuhinga 30: 99-177

ABSTRACT: New Zealand is a global centre of diversity for gadfly petrels (family Procellariidae, genus Pterodroma). The 11 extant breeding species include six endemic species (greyfaced petrel Pt. gouldi, Chatham Island tāiko/Magenta petrel Pt. magentae, mottled petrel Pt. inexpectata, Chatham petrel Pt. axillaris, Cook’s petrel Pt. cookii and Pycroft’s petrel Pt. pycrofti) and two further species of which more than 90% of the world population breeds in New Zealand (white-naped petrel Pt. cervicalis and black-winged petrel Pt. nigripennis). Within New Zealand, hotspots for Pterodroma species diversity include the Kermadec Islands (three species, none of which is endemic), islands off the northeast coast of the North Island (four species, three of which are endemic to New Zealand, with one endemic to the northeast North Island) and the Chatham Islands (three species, two of which are endemic to both New Zealand and the Chatham Islands). With the exception of the recently colonised soft-plumaged petrel Pt. mollis, all living New Zealand gadfly petrel species have suffered population declines and/or range contractions as a result of predation by introduced mammals (especially feral cats Felis catus and rats Rattus spp.), with nine of these 10 species recently responding positively to pest mammal eradications or species recovery programmes. Population sizes for each species range from about 35 known pairs for Chatham Island tāiko to more than 2.8 million pairs for black-winged petrel. Population trends are poorly known for most species, although eight species are considered to be stable or increasing.

KEYWORDS: gadfly petrels, Pterodroma, population sizes, population distribution, population trend, Procellariiformes, range, seabirds, New Zealand.