Chatham Island mollymawk
Thalassarche eremita Murphy, 1930
Other names: Chatham Island albatross, Chatham albatross, toroa, Chatham shy albatross, Chatham mollymawk
Geographical variation: Nil
The Chatham Island mollymawk is a rare albatross with a restricted range. It is striking in appearance, with a dark grey head and bright yellow bill. Endemic to the Chatham Islands, the entire population breeds on The Pyramid, an isolated, almost inaccessible rock stack located south of Pitt Island in the South Pacific Ocean. Truly a pelagic species they spend most of their life at sea only returning to land to breed.
The population is stable but vulnerable to severe storm events. Small numbers are caught as bycatch in domestic longline fisheries in New Zealand. However, they are vulnerable to longline fisheries off the coasts of Peru and Chile, where they migrate to outside the breeding season.
The Chatham Island mollymawk is an endemic medium-sized albatross from the Chatham Islands. Adults have a dark-grey head and neck, with white behind the eye and a thick black line in front of the eye extending towards the bill. The upperwings and back are blackish-brown, and the tail dark grey. The underparts and rump are white, and the underwings are white with a thin black edge (slightly thicker on leading edge) and a small black patch where the leading edge of the wing meets the body, and dark grey to black primaries. The bill is deep yellow with a black lower mandible tip. The legs and feet are light grey-flesh coloured. Immature Chatham Island mollymawks have a lighter grey head, variable amounts of grey on the underwing and undertail, and a yellowish-black bill with a black tip. Juveniles are similar to immature, but with a dark-grey bill with a black tip. Chicks have all light grey down and a black bill.
Voice: Chatham Island mollymawks are usually quiet at sea. They have a series of calls associated with breeding and territorial defence at colonies: bill clacking, harsh croaks and braying followed by aka aka aka calls.
Similar species: Adult Salvin’s mollymawks have a lighter grey head with a greyish-yellow bill (also with a dark tip to the lower mandible). Juveniles of Chatham Island, Salvin’s and Buller’s mollymawks are all similar, but are rarely seen in New Zealand waters, as all three migrate to seas off Chile and Peru after fledging. Buller’s mollymawk is smaller, with a less robust bill. Chatham Island mollymawk juveniles have the darkest ‘hood’, and generally show some yellow at the base of the bill.
Distribution and habitat
The Chatham Island mollymawk is a true pelagic species only returning to land to breed. The only breeding location is the isolated windswept 1.7 hectare rock stack, The Pyramid, located at the southern end of the Chatham Islands. One pair has attempted to breed on Western Chain, Snares Island. During the breeding season, Chatham Island mollymawks are commonly seen at sea around The Pyramid and the southern Chatham Islands and occasionally at sea around the eastern New Zealand coastline. They migrate to coastal waters off Chile and Peru outside their breeding season. There are records of vagrant Chatham Island mollymawks from eastern Australia, Tasmania and southern Africa.
The Chatham Island mollymawk has a stable annual population of about 5300 occupied nests on The Pyramid (based on surveys counting nest sites 1999-2010).
Threats and conservation
With only one breeding population, the Chatham Island mollymawk is vulnerable to severe storm events during the breeding season, which can affect breeding success and adult survival. Outside the breeding season such events can remove vegetation and the small amount of soil used for nest construction.
There is a history of occasional harvesting of Chatham Island mollymawks by Moriori and other settlers on the Chatham Islands. Although they do not normally follow fishing vessels, small numbers have been reported as bycatch in domestic longline fisheries in New Zealand. Chatham Island mollymawks are at greatest risk during the non-breeding season, from artisanal longline fisheries off the west coast of South America.
The Chatham Island mollymawk is currently listed as Naturally Uncommon by the New Zealand Department of Conservation and Vulnerable by the IUCN.
Chatham Island mollymawks breed in a single colony on The Pyramid, Chatham Islands. They are monogamous, annual breeders, with shared incubation and chick rearing. The single large (102 x 66 mm) whitish egg is laid on a nest pedestal, built of soil, guano, vegetation and occasionally bone that can reach up to 1m in height. Adults return to the colony in August, eggs are laid from mid September to late October, with incubation taking 68-72 days. Chicks hatch in November to December and fledge from March to May, when 120-140 days old.
Behaviour and ecology
Chatham Island mollymawks nests are built on rocky ledges and steep slopes, in close proximity, occupying almost all available space on The Pyramid. The steep slopes allow adults to land on or by their nest without disturbing other nesting birds. However, if intruders come too close to occupied nests the adults will act aggressively by biting, bill clacking or vomiting. Chicks respond to intruders by biting, bill clacking and regurgitating stomach oil.
Adult bonding and mating behaviour includes intricate pair displays and dances with raised heads, bowing and bobbing, braying calls followed by croak calls, dual bill clacking and rubbing, tail fanning, and mutual preening. Bonded pairs at nests during incubation and guard-stage shift changeovers display bray calls, dual bill clacking and rubbing, and mutual preening as mate recognition.
The earliest juveniles return to The Pyramid aged four years, with first breeding at seven years of age, but predominantly later with a peak at eleven years.
Salvin’s mollymawks have also been recorded on The Pyramid, where they interact with Chatham Island mollymawks, with one mixed species pair recorded on a nest together, caring for a chick.
At sea Chatham Island mollymawks are generally solitary and don’t tend to follow ships. They form rafts up to several hundred individuals in washing flocks, offshore from The Pyramid.
Chatham Island mollymawks are generally surface feeders, but will shallow dive for food. They are known to feed on fish, squid and krill.
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Chatham Island mollymawk
- Social structure
- Breeding season
- Nest type
- Nest description
- Pedestal of soil, guano and vegetation.
- Nest height (min)
- 0 m
- Nest height (max)
- 1 m
- Clutch size (mean)
- Mean egg dimensions (length)
- 101.6 mm
- Mean egg dimensions (width)
- 65.5 mm
- Egg colour
- Egg laying dates
- Interval between eggs in a clutch
- Not applicable days
- Incubation behaviour
- Incubation length (mean)
- 68-72 days
- Incubation length (min)
- 68 days
- Incubation length (max)
- 72 days
- Nestling type
- Nestling period (mean)
- 120-140 days
- Nestling period (min)
- 120 days
- Nestling period (max)
- 140 days
- Age at fledging (mean)
- 120-140 days
- Age at fledging (min)
- 120 days
- Age at fledging (max)
- 140 days
- Age at independence (mean)
- 120-150 days
- Age at independence (min)
- 120 days
- Age at independence (max)
- 150 days
- Age at first breeding (typical)
- 7 plus years
- Maximum longevity
- > 30 years
- Maximum dispersal
- > 10,000 km