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The wooded hills and scarps of Punakaiki behind the Barrytown Flats, Westland, New Zealand are home to the ACAP-listed and Vulnerable Westland Petrel Procellaria westlandica.

Punakaiki is located c. 60 km north of Greymouth, in the South Island of New Zealand.  The hills are clothed in a dense forest of mixed podocarp forest, including the trees Rata Trosideros sp., Miro Prumnopitys ferruginea and Matai P. taxifolia and tree ferns.  The understorey is a dense tangle of vines, especially Supple-jack Ripogonum scandens and Kiekie Freycinetia banksii.

The climate at the breeding sites is sub-tropical, with very occasional frosts. The high rainfall in the area makes it a damp and challenging environment for agriculture or other industry, hence the region is sparsely populated.  Large parts are protected in natural reserves or national parks.

The Westland Petrel breeding area is largely contained within a Specially Protected Area which abuts the Paparoa National Park on its northern edge.  Other boundaries are adjacent to private land and areas zoned for agriculture, low-density housing or other development. Currently there are no industrial sites in adjoining areas.

Although the risk of mining activity for ilmenite in the area has long been known, the reality of this has come and gone with the flux of economic drivers on resource exploitation.  It appears currently that this possibility is still being actively considered.  If developed, a large industrial complex within the flight path of the birds along the Barrytown Flats poses a strong risk of birds being attracted to the lights of the mineral-production area, and becoming disoriented, crushed by machinery or trapped in areas from which they could not take off.

The region in which the petrels currently breed was actively mined from the mid-to-late 1800s, when it was progressively turned over to sheep and cattle farmland, and was logged until the 1980s.  Although these activities occurred on the margins of the main breeding colonies, as we know them today, direct impacts of harvesting and depredation by domestic dogs may have had a strong influence on the population historically.  Farming activities encroached on the colony areas nearest the sea, but since the 1990s have become increasingly redundant on the steeper slopes and wooded areas, and progressively the land abutting the main petrel nesting areas has been added into protected or adjoining quasi-protected areas (e.g. Regional Council Significant Natural Areas).  There are no huts or roads to the colony, and access is by foot and requires permits.  Muttonbirding, a concern for fledging success raised in the 1970s, seems to be in abeyance.

Several introduced mammals are known to occur in the petrel colonies, including Brush-tail Possums Trichosurus vulpecula, rats, dogs, goats and Stoats Mustela erminea.  All of these cause problems for soil stability (browsing species) and/or direct predation of the nesting petrels, particularly of their young.

The Westland Petrel is the only ACAP-listed species to breed at this site, which is the only breeding site for the species.  Population estimates of c. 4000 pairs have been recorded in two recent surveys during 2004-06.

Westland Petrels breed in burrows c. 1.2 m long at a density of 0.21 – 0.26/m².  They nest under trees and tree-ferns or in dense patches of vines or Kiekie.  In the frequently-used colony areas, the undergrowth is removed and bare soil is exposed year round.  Colonies of 50 – 300 burrows are most common, and one large colony of c. 1000 burrows is utilized as the main study colony for demographic research.

The birds frequent the colony for over nine months of the year, arriving in March for pre-nuptial displays, laying in late May to early June, with chick rearing commencing in the last weeks of July.  Chicks are fed until November.

Photographs by Jean-Claude Stahl and Susan Waugh.

Selected References:

Baker, A.J. & Coleman, J.D. 1977.  The breeding cycle of the Westland Black Petrel (Procellaria westlandica). Notornis 24: 211-231.

Baker, B., Cunningham, R., Hedley, G. & King, S. 2008.  Data Collection of Demographic, Distributional and Trophic Information on the Westland Petrel to allow Estimation of Effects of Fishing on Population Viability.  Unpublished Report Prepared for the Ministry of Fisheries PRO2006-01H.  Kettering: Latitude 42 Environmental Consultants.

Waugh, S.M., Wood, G.C. & Davis, L.S. 2003.  Burrow occupancy in Westland Petrels (Procellaria westlandica).  Notornis 50: 123-127.

Waugh, S.M. & Bartle J.A. 2013.  Westland Petrel.  In: Miskelly, C.M. (Ed.)  New Zealand Birds Online.

Waugh, S.M., Doherty, P.F., Freeman, A.N.D., Adams, L.; Woods, G C., Bartle, J.A. & Hedley, G.K. 2006.  Demography of Westland Petrels (Procellaria westlandica), 1995-2003.  Emu 106: 219-226.

Wood, G.C. & Otley, H.M. 2013.  An assessment of the breeding range, colony sizes and population of the Westland Petrel (Procellaria westlandica).  New Zealand Journal of Zoology 40: 186-195.

Susan Waugh, Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand, 17 October 2013