Westland petrel (Procellaria westlandica)

KingdomAnimalia
PhylumChordata
ClassAves
OrderProcellariiformes
FamilyProcellariidae
GenusProcellaria (1)
SizeLength: 50 – 55 cm (2)
Wingspan: 135 – 140 cm (2)
Weight800 – 1200 kg (2)

Classified as Vulnerable (VU) on the IUCN Red List 2006 (1) and listed on Appendix II of the Convention on the Conservation of Migratory Species (CMS) (3).

This large, marine bird is extremely similar in appearance to the white-chinned petrel; both are bulky, almost entirely black, with black legs and feet, and a pale ivory-yellow bill, which is whiter in juveniles. However, the bill of the Westland petrel has a black tip. There are no noticeable differences between the male and the female (2) (4). When at its breeding colony the Westland petrel can be heard making staccato, wheezy, moaning calls (4).

The Westland petrel breeds only in New Zealand, at Punakaiki on the South Island. When not breeding, it can be found in the eastern and central Pacific Ocean, and in waters off South America (4).

As a marine bird, it is generally found over the ocean, except when breeding, when it nests in densely forested hills, at elevations between 20 and 250 m (2) (4).

The Westland petrel is one of the largest burrowing petrels, and one of the few petrel species that still breed on the New Zealand mainland, probably as their larger size makes them less vulnerable to mainland predators than smaller petrel species (5) (6). They build large, cavernous burrows in colonies, up to 2 m long, close to steep slopes, cliff edges or trees from where they can take off (7). In May (8), one egg is laid in the burrow and incubated for 57 to 65 days (2). Chicks fledge after 120 to 140 days and then head out to the open ocean, not returning to the colony for five years, and not breeding themselves until, on average, the age of ten (2) (6) (8).

When not breeding, they forage out over the ocean, feeding on cephalopods, fish and crustaceans (2). Westland petrels feed primarily by day (8). They most frequently feed by sitting on the water and seizing prey with their bill, but they can also dive well, propelling themselves with their powerful wings (2). Westland petrels are also eager scavengers; they are frequently found following fishing vessels, where they feed on fisheries waste which forms a substantial part of its diet (2) (4).

Like many other New Zealand birds the Westland petrel is threatened by introduced mammals, which prey on eggs, chicks and adults, and trample burrows. The main threats ashore are cats (which prey on chicks near fledging) and stray dogs (which may dig adults from burrows) (8). Mining, agriculture and timber milling activities have cleared areas of forest, reducing the amount of available breeding habitat, and disturbing the petrels already breeding. Street-lights in conjunction with electricity lines along the adjacent highway regularly kill small numbers of departing fledglings and adults (8).

At sea, the primary threat to the Westland petrel, like other petrels and albatrosses, is the activities of the fishing industry. Some are drowned by tuna longline fishing boats in New Zealand and by longliners in South American waters. Tuna longlining is a fishing method that can involve a single line up to 130 km long, with thousands of baited hooks attached to it, set from behind a boat. Petrels, scavenging in the ocean, try to eat the bait from the line as it is set behind the boat, but instead swallow the hooks and are dragged under and drowned (2) (4).

The Westland petrel is listed on Appendix II of the Convention on Migratory Species, and is subsequently part of the Agreement on the Conservation of Albatrosses and Petrels (ACAP). ACAP aims to stop or reverse population declines in 28 species from the southern hemisphere, by coordinating action between range states to mitigate known threats to albatross and petrel populations. An action plan has been drawn up which describes a number of conservation measures to be implemented including research and monitoring, reducing fisheries-related mortality, eradicating non-native species at breeding sites, and reducing habitat loss, disturbances and pollution (9).

The breeding site at Punakaiki lies within the Paparoa National Park, which offers the Westland petrel a degree of protection, and the behaviour, breeding biology and social organisation of this population has been studied since 1969 (4). Predators on the South Island are also actively controlled every year by the New Zealand Department of Conservation (8). However, further measures to protect this rare bird have been recommended, such as constructing fences around the breeding colony to exclude mammals (4).

For further information on the conservation of the Westland petrel see the Agreement on the Conservation of Albatrosses and Petrels:
http://www.acap.aq/

For further information on the threat of longlining to seabirds and the solutions see Save the Albatross:
http://www.savethealbatross.net/

For more information on this and other bird species please see:

Authenticated (07/08/07) by Sandy Bartle, Curator of Birds, Museum of New Zealand Te Papa Tongarewa.

  1. IUCN Red List (January, 2007)
    http://www.iucnredlist.org
  2. del Hoyo, J., Elliott, A. and Sargatal, J. (1992) Handbook of the Birds of the World. Vol. 1: Ostrich to Ducks. Lynx Edicions, Barcelona.
  3. CMS (January, 2007)
    http://www.cms.int
  4. Birdlife International (May, 2007)
    http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=3924&m=0
  5. Te Ara – The Encyclopedia of New Zealand (May, 2007)
    http://www.teara.govt.nz/EarthSeaAndSky/BirdsOfSeaAndShore/Petrels/3/en
  6. New Zealand Birds (May, 2007)
    http://www.nzbirds.com/birds/petrelwestland.html
  7. Brooke, M. (2004) Albatrosses and Petrels across the World. Oxford University Press, Oxford.
  8. Bartle, S. (2007) Pers. comm.
  9. CMS (May, 2007)
    http://www.cms.int/species/acap/acap_bkrd.htm