Volume 45, No. 2

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Threats and threat status of the Westland Petrel Procellaria westlandica


1Museum of New Zealand Te Papa Tongarewa, PO Box 467, Wellington 6012, New Zealand (
2West Coast Penguin Trust, PO Box 70, Charleston 7865, New Zealand


WAUGH, S.M. & WILSON, K-J. 2017. Threats and threat status of the Westland Petrel Procellaria westlandica. Marine Ornithology 45: 195 - 203

Received 21 June 2017, accepted 21 July 2017

Date Published: 2017/10/15
Date Online: 2017/10/09
Key words: habitat degradation, New Zealand, predation, threat assessment, Westland Petrel


Threat status assessments provide a benchmark for identifying priorities for conservation and related research for special-status species. We review data about an endemic New Zealand seabird, the Westland Petrel Procellaria westlandica, and provide information to assist future threat assessment reviews. A range of threats have potential or have already contributed to reductions in population growth at a level that may exceed 10% over 10 years (ranked 'High' or 'High potential' threats). The realised (observed) threats include landslips and extreme climate events that degrade nesting habitat; bycatch mortality in commercial, recreational, and high-seas fisheries; attraction of fledglings to lights; and the potential encroachment of pigs Sus scrofa and dogs Canis familiaris into breeding areas. Low-ranked threats (which may contribute <10% to population reduction over 10 years) include habitat degradation by browsing introduced mammals and land development; death of individuals by striking wires or buildings; disturbance at colonies; the petrels' consumption of fisheries waste and plastics; human harvest; and naturally occurring mortality such as predation by native species or entrapment in tree branches and vines. Population size estimation, demographic modelling, and trend information indicate that the population is small (~2800 breeding pairs), with very low productivity and therefore potential vulnerability to stochastic events. Recent surveys show that the area of breeding habitat occupied by the birds is only about 0.16 km2. Storm events in 2014 severely reduced habitat quality, destroyed large parts of some colonies, and increased the likelihood of further erosion and landslip for at least 75% of the global breeding population. Storm impacts at other colonies have not yet been assessed. In light of this information, we recommend immediate review of the threat status of the species and initiation of mitigation to reduce the severity of threats. The information available indicates that a relisting to IUCN Endangered status may be warranted, and that the Agreement on the Conservation of Albatrosses and Petrels threat assessments should be revised to include two high-level potential threats: pig predation and dog predation.


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