An assessment of the breeding range, colony sizes and population of the Westland petrel (Procellaria westlandica)

Abstract

The Westland petrel (Procellaria westlandica) is an endemic New Zealand species and one of the very few burrowing seabird species still breeding on mainland New Zealand. It nests only on a series of coastal ridgelines near to Punakaiki on the West Coast of the South Island. Between 2002 and 2005, surveys were undertaken at 28 of the 29 known colonies. The area occupied by the colonies was 73 ha; most colonies had fewer than 50 burrows, but six colonies had 201–500 burrows and four colonies had more than 1000 burrows. We find that the current breeding range of Westland petrel and the location of individual colonies are similar to those reported in both the 1950s and 1970s. Based on total burrow counts at 28 colonies and burrow occupancy rates determined by annual monitoring, the annual breeding population is estimated to be between 2954 and 5137 breeding pairs.

Keywords:

• Westland petrel
• Procellaria westlandica
• seabird
• burrow
• population
• census
• New Zealand

Acknowledgements

Many thanks to the following surveyors who assisted with fieldwork: Martin Abel, Sonya Roxburgh, Jane Prendergast, Lisa McArthur, Barry Chalmers, Reuben Lane, Daniel Sawyers, Mark Jones, Bevin Cairns, Nicki Winslade and Robert Schadewinkel. Department of Conservation staff Martin Abel managed the Westland petrel programme, and Liam Anderson and Cielle Stephens produced Fig. 1. Tim Shaw, John Lyall, Paul Scofield, Richard Phillips and Graeme Taylor provided very useful advice for earlier drafts. Jonathon Banks, Amanda Freeman and one anonymous referee helped to improve the manuscript.