Campbell Island teal (Anas nesiotis)
|Also known as:||Campbell Island flightless teal|
|Synonyms:||Anas aucklandica nesiotis|
|Size||Male wingspan: 128 – 138 cm (2)|
Female wingspan: 114 – 125 cm (2)
Male weight: 290 – 500 g (2)
Female weight: 280 – 265 (2)
The Campbell Island teal is classified as Endangered (EN) on the IUCN Red List (1) and listed on Appendix I of CITES (3).
Once thought to be extinct, the Campbell Island teal (Anas nesiotis) is now believed to be one of the world’s rarest ducks, after just 20 individuals were found on Dent Island in 1975 (4). One of the few remaining flightless birds in the world, this duck is a product of an island environment isolated from the rest of the world for more than 80 million years, and free from mammalian predators. To compensate for its lack of flight, the Campbell Island teal can run very rapidly along the ground when disturbed (4) (5).
Breeding males are a dark sepia colour, with strong green iridescence on their head, neck and back, dark chestnut tones on the breast, and lighter plumage on the abdomen, in addition to a conspicuous white ring around the eye and obvious white tail spot. During non-breeding plumage, the iridescence on the head and back becomes less intense, the tail spot becomes indistinct and the eye ring becomes pale fawn. Females are uniformly dark brown with a paler abdomen, and prominent white eye ring (2). The call involves a series of soft, high-pitched whistles from the male, and low quacks and growls from the female (6).
Endemic to New Zealand, the Campbell Island teal is confined to the 23 hectare Dent Island, an offshore islet of Campbell Island (6). Campbell Island is thought to have been a stronghold for the species in the past, before becoming extinct there over 180 years ago (6) (7). In 1990, a survey of Dent estimated a population of 60 to 100 birds, probably equating to no more than 25 breeding pairs (6). In 1999 and 2000, a total of 24 captive-bred birds were released on Codfish Island but have since been removed, and in 2004 and 2005 a total of 105 birds were released on to Campbell Island (4).
Found under thick, chest-high tussock grass. The Campbell Island teal is sighted over most of the island but probably more common below 100 metres, and in damp areas (6).
There has been no biological study of the Campbell Island teal on Dent Island, with most knowledge of the bird coming from captive or post-release populations (8). Clutches are small compared to most ducks, consisting of one to five eggs, with a typical clutch size of three or four (6). In captivity, these are laid from October to January. The gestation period lasts for 30 to 34 days and both sexes can breed at one year (2). Campbell Island teal generally live to about 10 years, usually in pairs or small flocks (9). Pairs appear to demonstrate territoriality year round (2).
This nocturnal bird has not been observed feeding on Dent Island, but feeds on amphipods, weevils, earthworms, seaweed and other insects in captivity, and has been seen eating invertebrates in piles of rotting seaweed on Codfish Island (6).
Having disappeared from much of its former range, the Campbell Island teal population reached critically low numbers and has clung to a precarious existence. This bird’s extirpation from it presumed former stronghold, Campbell Island, has largely been attributed to predation by introduced Norway rats (Rattus norvegicus) that got ashore from sealing and whaling ships in the early 19th Century (4). Present-day potential threats include the accidental introduction of predators or avian disease to Dent Island, the bird’s last natural refuge, or even severe weather conditions, which could have a catastrophic effect (6). Indeed, with such a small current population and limited natural range, this bird is now extremely vulnerable; just a single event is capable of driving it to complete extinction (5).
The outlook for the Campbell Island teal looked bleak when first rediscovered in 1975, but thankfully since then there has been fantastic progress with captive breeding programmes and the population has increased to a healthier, though still unstable, level (5). Captive breeding was started by New Zealand’s Department of Conservation in 1984, from three males and one female taken from the small population on Dent Island, and another four males and three females captured in 1990. The first duckling finally hatched in 1994 at the Pukaha Mt Bruce National Wildlife Centre, receiving international attention, and by 2000 the captive population had reached 60 (4). The Department of Conservation initially released a total of 24 captive-bred birds on to the predator-free Codfish Island in 1999 and 2000 as an insurance population, and to be eventually used to restock Campbell Island (4) (5). These had an 88 percent survival rate. With this success, the Department of Conservation decided to translocate captive-bred birds directly to Campbell Island, made viable by a successful rat and cat eradication programme in 2001 (4). Thus, 50 teal, including 28 from Pukaha Mount Bruce and 22 from Codfish Island were released onto Campbell Island in September 2004, and a further 55 in September 2005 and 54 in 2006 (4) (5). A check in February 2005 found no evidence that the first batch of released birds had bred, but this may be due to their being moved close to the breeding season (4). Two decades of conservation effort have brought this bird back from extinction on Campbell Island, and meant that it now has a good chance of being able to recover and thrive once more in its native home (7).
For further information on the Campbell Island teal:
- Williams, M. (2005) Campbell Island Teal Anas nesiotis Species Account. In: Kear, J. (Ed.) Ducks, Geese and Swans: Anseriformes (Bird Families of the World S.). Oxford University Press, Australia and New Zealand.
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- Amphipoda: order of crustaceans.
- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Gestation: the state of being pregnant; the period from conception to birth.
- Invertebrates: animals with no backbone.
- Nocturnal: active at night.
IUCN Red List (June, 2011)
- Williams, M. (2005) Campbell Island Teal Anas nesiotis Species Account. In: Kear, J. (Ed) Ducks, Geese and Swans: Anseriformes (Bird Families of the World S.). Oxford University Press, Australia and New Zealand.
CITES (November, 2005)
TerraNature (November, 2005)
Department of Conservation (June, 2008)
BirdLife International (November, 2005)
Pukaha Mount Bruce (November, 2005)
- Seddon, P.J. and Maloney, R.F. (2003) Campbell Island teal re-introduction plan. Department of Conservation, Wellington, New Zealand.
Wellington Zoo (November, 2005)