a subspecies of the black petrel (Procellaria parkinsoni), but it was soon classified as a separate species. The male holotype specimen, collected at Barrytown on 29 April 1946, is held at the Canterbury Museum. The Māori name is tāiko, which also refers to the black petrel, Procellaria parkinsoni. Description The adult Westland petrel is a stocky bird, weighing around . It is entirely dark blackish-brown, with black legs and feet. Some individuals may have a few white feathers. The is pale yellow with a dark tip. Falla measured the female and male birds for his original description and pointed out that the male of the species measured slightly larger than the female. However the female specimen weighed slightly more than the male. It is one of the largest of the burrowing petrels. Falla described the eggs of this species as follows: Moulting occurs in the Westland petrel in their non-breeding season between October and February, during migration to South America. The immature birds moult before older individuals do. Distribution and habitat The Westland petrel is endemic to New Zealand. It spends most of its life at sea, only returning to land to breed, and breeds only in a small region of the South Island's West Coast. The breeding range covers an wide strip between Barrytown and Punakaiki, specifically from the Punakaiki River to Waiwhero (Lawson) Creek. The area of the breeding colonies comprises forest-covered coastal foothills within the Paparoa National Park, or other conservation land, or on land belonging to Forest And Bird. There is also a breeding colony located on private land. The total area of all breeding colonies combined is only about . During the breeding season, adults may be seen in waters around New Zealand from Cape Egmont to Fiordland in the west, through the Cook Strait, and from East Cape to Banks Peninsula in the east. Westland petrels also range across areas of the Pacific Ocean and Tasman Sea around the subtropical convergence. In the non-breeding season, the birds migrate east to waters off South America and feed in the Humboldt Current. They are often found in waters to the west of the Chilean coast. Individuals usually remain solitary during this time, rejoining the colony when the next breeding cycle begins. Breeding and life-cycle The Westland petrel is one of the few petrel species that still nest on the mainland. Their large size and aggressive behaviour