Chatham petrel (Pterodroma axillaris)
|Also known as:||Chatham Island petrel, Chatham Islands petrel|
|Size||Length: 30 cm (2)|
Wingspan: 63 - 71 cm (3)
|Weight||200 g (2)|
The Chatham petrel is classified as Endangered (EN) on the IUCN Red List (1).
The Chatham petrel (Pterodroma axillaris) is a small, slight seabird, endemic to the Chatham Islands, New Zealand. It has white underparts, grey upperparts, and a moderately distinct dark grey ‘M’ shape across the upperwing. Its head is dark grey with black markings around the eyes and the tail is grey with a darker tip (4).
The Chatham petrel looks very similar to the black-winged petrel (Pterodroma nigripennis) (2), but it can be distinguished by a broad, black bar on the underwing which extends from the body towards the wing tip, whereas in the black-winged petrel the underwing bar does not extend to the body (4).
In flight, the Chatham petrel calls ‘whis-whis-whis, oi’and it gives a purring call when on the ground (4).
Subfossil evidence suggests that the Chatham petrel was once widespread throughout the Chatham Islands, New Zealand, with records from Chatham, Pitt and Mangere Islands (5) (6).
However, in recent times, the Chatham petrel has been restricted to a single breeding site on Rangatira Island. A small breeding colony has now been established on Pitt Island, and it is hoped that transfers to Chatham Island will also be successful (5).
Based on the behaviour of closely related species, the Chatham petrel possibly migrates to the North Pacific Ocean between June and October (7) (8). However, sightings of the Chatham petrel have been recorded at sea to the south of the Chatham Islands (9).
This pelagic bird nests in burrows on sloping ground in lowland temperate forest and scrub (4). The Chatham petrel seems to prefer burrows under mature forest cover, and the main nesting sites on Rangatira Island are in the Kokupu Creek headwaters (7). Much of the rest of the year is spent out at sea (4).
The Chatham petrel is capable of fast, agile flight. It forages mainly in the open ocean (7), and its diet, although not well understood, is thought to include fish and squid (4) (7).
The breeding season lasts from November until June (7). The Chatham petrel returns to land from November, laying a single white egg between December and February. The egg is incubated for six to eight weeks, and the male and female Chatham petrel both contribute to incubation and chick raising (7). The chicks fledge between May and June (8).
The Chatham petrel usually forms a pair bond which it maintains from year to year, although disruptions to pair bonding can occur, for reasons not well understood (7). Individuals do not usually breed until five years old, although breeding has been recorded as early as age three (4).
The main threat to the Chatham petrel is competition for burrows with the broad-billed prion (Pachyptila vittata), which breeds earlier in the year, leaving the Chatham petrel at a competitive disadvantage (7). The broad-billed prion is also known to attack eggs, chicks and occasionally adults, causing burrow evictions and high rates of mortality in young Chatham petrels (10). Broad-billed prion interference has also been proposed as a contributing factor in pair bond disruption (4).
Human exploitation, loss of forest habitat, and introduced mammalian predators, especially rodents and cats, have all contributed to the decline in the Chatham petrel population on Rangatira and the local extinction of this bird on the other islands in the Chatham group (11). Invasive alien mammal species have been eradicated on Rangatira, but reinvasions remain a potential threat to the Chatham petrel (7).
Intensive research into the reasons for the decline of the Chatham petrel in the last two decades has led to several conservation actions. Breeding burrows have been artificially blockaded to prevent occupation by the competing broad-billed prion, and any prions found invading petrel burrows during absences are culled. Installation of neoprene flaps to burrow entrances has helped reduce broad-billed prion interference during the incubation period, and continual burrow monitoring and artificial nest site protection has significantly improved Chatham petrel breeding success (11).
Furthermore, following recommendations outlined in the Chatham Petrel Recovery Plan, two new populations of Chatham petrels have been established in protected reserves to reduce the inherent risk of the devastating impact of disease or natural disaster on a single population (7). Between 2002 and 2005, 200 petrel chicks were translocated to the Ellen Elizabeth Preece Conservation Covenant (EEPCC) on Pitt Island, with some since having been identified as returning and successfully rearing chicks. In 2008, another translocation of 47 petrel chicks occurred to Sweetwater Conservation Covenant on Chatham Island, with the hope of similar successes as those in the Pitt Island translocation (12). Constant management and protection of translocated Chatham petrel populations from invasive alien predators will remain necessary unless eradication also occurs on other islands (4).
More information on the Chatham petrel:
BirdLife International - Chatham petrel:
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- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Incubation: the act of incubating eggs, that is, keeping them warm so that development is possible.
- Invasive alien: species introduced deliberately or unintentionally outside their natural habitats where they have the ability to establish themselves, invade, outcompete natives and take over the new environments.
- Pelagic: in birds, applied to sea birds that come to land only to breed, and that spend the major part of their lives out at sea.
- Temperate: referring to the geographical region that lies between the polar and tropical regions, characterised by a moderate climate with distinct seasons.
- Translocated: when individual living organisms from one area have been transferred and released or planted in another area.
IUCN Red List (November, 2011)
- Robertson, H.A. and Heather, B.D. (2001) The Hand Guide to the Birds of New Zealand. Oxford University Press, USA.
- del Hoyo, J., Elliott, A. and Sargatal, J. (1992) Handbook of the Birds of the World. Vol. 1: Ostrich to Ducks. Lynx Edicions, Barcelona.
BirdLife International (November, 2011)
Department of Conservation - Chatham petrel (November, 2011)
- Tennyson, A.J.D. and Millener, P.R. (1994) Bird extinctions and fossil bones from Mangere Island, Chatham Islands. Notornis (Supplement), 41: 165-178.
Aikman, H., Davis, A., Miskelly, C.M., O'Connor, S. and Taylor, G.A. (2001) Chathampetrel Recovery Plan 2001-2011. Threatened Species Recovery Plan 37. Department of Conservation, Wellington, New Zealand. Available at:
- Gardner, P. (1999) Aspects of the breeding biology of the Chatham petrel (Pterodroma axillaris). Science for Conservation, 131: 5-21.
- West, J.A. (1994) Chatham petrel (Pterodroma axillaris) an overview. Notornis (Supplement), 41: 19-26.
- Was, N.W., Sullivan, W.J. and Wilson, K.-J. (2000) Burrow competition between broad-billed prions (Pachyptila vittata) and the endangered Chatham petrel (Pterodroma axillaris). Science for Conservation, 167: 5-41.
- Taylor, G. (2000) Action plan for seabird conservation in New Zealand. Part A: threatened seabirds. Department of Conservation: Biodiversity Recovery Unit, Wellington, New Zealand.
- Miskelly, C.M., Taylor, G.A., Gummer, H. and Williams, R. (2009) Translocations of eight species of burrow-nesting seabirds (genera Pterodroma, Pelecanoides, Pachyptila and Puffinus: Family Procellariidae). Biological Conservation, 142: 1965-1980.