White-necked Petrel (Pterodroma cervicalis)

White-necked Petrel

Subspecies

Genus	Species	subspecies	Region	Range
Pterodroma	cervicalis		PO	w

Genus

Genus Pterodroma, Pseudobulweria and Aphrodroma are also knwon as the Gadfly Petrels. They vary in size from rather small birds such as the Cookilaria-species, measuring about 26 cm, to the much larger and robust representatives of this group like the White-headed Petrel with an overall length of about 43 cm. Their plumages also vary a great deal from species to species; from completely black to light grey mantles and pure white bellies, and with different color phases within species. One feature shared by all of them is the black bill of which the shape also shows much variation. Some species are extremely rare and restricted to a very limited area, other are abundant and wander widely or have unknown pelagic ranges.
The group of the Gadfly Petrels counts over 35 species, mainly from the Southern Hemisphere. There are three genera: Pterodroma with about 30 species, Pseudobulweria counting four and Aphrodroma with only one. Many authors have tried to classify the large number of species of this group and to determine their relationships. This has resulted in a division in several subgenera and the grouping of several species which are considered to have a more or less close relationship. The taxonomic discussion has not come to an end yet: new species have been added or split recently and probably will be in the near future.

Physical charateristics

Large, grey-and-white petrel with distinctive white hindneck. Black cap extends to below eyes. White band extends from throat around hindneck. Grey upperparts, upperwing, with black “M” across wings. May have grey half-collar across upper breast. White underparts. White underwing with narrow, black trailing edge, black tip, wider black leading edge distal to carpal joint, short, bolder black bar extending towards centre of wing from joint. Distinguished from Juan Fernandez Petrel P. externa by stronger cap contrast, bolder black marking at leading edge of underwing distal to carpal joint. P. externa has grey nape, but some individuals become almost as white-necked as P. cervicalis.

wingspan min.:	95	cm	wingspan max.:	105	cm
size min.:	42	cm	size max.:	46	cm
incubation min.:	0	days	incubation max.:	0	days
fledging min.:	100	days	fledging max.:	115	days
broods:	1		eggs min.:	1
			eggs max.:	1

Range

Pacific Ocean : West. Pterodroma cervicalis breeds on Macauley Island in the Kermadec Islands, New Zealand (c.50,000 pairs in 1988, Pacific Oceanssibly increasing), with a second small colony still present on Phillip Island, off Norfolk Island (to Australia) (a few breeding pairs). It is also reported to breed on Mere Lava in Vanuatu where it is well known to local communities. It bred on Raoul Island, also in the Kermadec Islands, early in the 20th century. It migrates to the north Pacific Ocean1, with a recent sighting off Gau Island, Fiji.

Habitat

On Macauley, it nests in burrows, generally on high, gently sloping areas with sedges and grass. On Raoul, it nested below 300 m on high-altitude ridges.

Reproduction

Little is known of the breeding biology. Breeds in colonies along with other conspecifics. Builds nest in burrows, clutsch size one egg, incubation period unknown. The young flegde after about 14 to 16 weeks.

Feeding habits

It feeds mainly on squid

Video White-necked Petrel

httpv://www.youtube.com/watch?v=AB_xJpioIa0

Conservation

This species qualifies as Vulnerable because it has a very small range, on two or three very small islands, and it is therefore susceptible to stochastic events and human impacts.
The population on Raoul was probably destroyed by feral cats and brown rat Rattus norvegicus. The Pacific rat R. exulans is present on Macauley, but does not apparently attack eggs or chicks. Feral goats were present on both Raoul and Macauley and trampled burrows. Rabbits were formerly present on Phillip, and extensive grazing and burrowing caused large-scale erosion. It remains vulnerable to the introduction of further mammalian predators, and also to fire and disturbance by visitors. The species is potentially threatened by climate change because it has a geographically bounded distribution: it is restricted to an island or islands with a maximum altitude of 238 m.

Migration

Transequatorial migrant, ranging over tropical and subtropical waters of NW Pacific, N to Japan; abundant in C Pacific May-Nov, where some birds occur all year round.

Distribution map

White-necked Petrel distribution range map

Planet of Birds