01681nas a2200229 4500008004100000245016500041210006900206300001000275490000700285520082200292653002401114653001301138653002201151653001401173653003901187653001701226100001501243700002101258700002001279700001901299856013301318 2003 eng d00aAn estimate of numbers of grey-faced petrels ( Pterodroma macroptera gouldi ) breeding on Moutohora (Whale Island), Bay of Plenty, New Zealand, during 1998-20000 aestimate of numbers of greyfaced petrels Pterodroma macroptera g a23-260 v503 aAbstract Moutohora (Whale Island) holds the largest surveyed breeding colony of grey-faced petrels (*Pterodroma macroptera gouldi*). For our estimate of the breeding population, we divided the island into 16 sections within which burrow densities were approximately uniform; the surface areas of these sections were found by planimetry. Apparently completed burrows were counted in 1998-2000 within each section by plots of 2 m radius along linear transects, or by 10 X 10 m contiguous plots. The total estimate (± SE) for the island was 109,000 * 10,000 burrows, which equates to about 95,000 pairs breeding annually, given an occupancy rate of about 87%. The population has apparently more than doubled since Norway rats (Rattus norvegicus) and rabbits (Oyctolagus cuniculus) were eradicated in 1985/87.10abreeding population10aestimate10aGrey-faced Petrel10aMoutohora10apost-predation population recovery10aWhale Island1 aImber, M J1 aHarrison, Malcom1 aWood, Saskia, E1 aCotter, Reg, N uhttp://notornis.osnz.org.nz/estimate-numbers-grey-faced-petrels-pterodroma-macroptera-gouldi-breeding-moutohora-whale-island-bay