Chatham Petrel (Pterodroma axillaris)

Chatham Petrel

Subspecies

Genus	Species	subspecies	Region	Range
Pterodroma	axillaris		PO	sw

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

Small, grey-and-white gadfly petrel with unique underwing pattern. Dark grey crown, sides of face and neck. Black mark behind eye. Grey upperparts. Grey tail with dark tip. Grey upperwing with dark, moderately distinct “M”. Pale grey half-collar at sides of breast. Rest of underparts white. White underwing with dark tip, broad, black bar extending from axillaries (where broadest) to carpal joint, then less prominently towards tip.

wingspan min.:	0	cm	wingspan max.:	0	cm
size min.:	28	cm	size max.:	32	cm
incubation min.:	45	days	incubation max.:	49	days
fledging min.:	83	days	fledging max.:	86	days
broods:	1		eggs min.:	1
			eggs max.:	1

Range

Pacific Ocean : Southwest. Pterodroma axillaris is restricted to South East Island (= Rangatira) in the Chatham Islands, New Zealand

Habitat

It nests in burrows in very friable densely burrowed soils in lowland temperate forest and scrub, on flat to moderate sloping ground

Reproduction

It nests in burrows in very friable densely burrowed soils in lowland temperate forest and scrub, on flat to moderate sloping ground. Its diet is not well known but includes squid and small fish. Some young have returned to the island at two years old, and breeding has been recorded at age three, though most individuals do not breed until age five11. Much of the life cycle is spent at sea; birds return to land only to breed. Visits to the colony are after dark. Nests are built in burrows which are firstly visited from the middle of Novembe. Preparing the nest, cortushiop and pairing takes about four weeks. Incubation length is about 47 days and is comparable with similar-sized gadfly petrels. Chatham petrel chicks fledge at about 85 days and are abandoned for approximately 11 days prior to fledging.

Feeding habits

Its diet is not well known but includes squid and small fish

Conservation

This species has been listed as Endangered as it has a small population which has undergone very rapid declines over the past three generations. The population stabilised and has begun to increase since 2000; a trend boosted by two recent translocations.
Pterodroma axillaris is restricted to South East Island (= Rangatira) in the Chatham Islands, New Zealand, although subfossils indicate that it was once more widespread, being present on Chatham, Pitt and Mangere Islands. The earliest estimate of 50 birds was later revised to 200-400. In 2004 the global population stood at 1,000-1,100 individuals comprising the 250 breeding pairs, a floater population of adults unable to breed each year owing to loss of partners or nesting sites, and juveniles aged 0-5. The increase reflects an improvement in knowledge and since 2000, a marked response to successful management with over 100 chicks now fledging annually and many recruiting back to the island.

Migration

Unknown; absent from colonies Jun-Nov. Single recent record outwith breeding grounds c. 120 km S

Distribution map

Chatham Petrel distribution range map

Planet of Birds