VU
Campbell Teal Anas nesiotis



Justification

Justification of Red List Category
Although this species's population size is increasing, it is restricted to two small subpopulations and the introduction of rats to Campbell Island or Whenua Hou could lead to rapid declines and push the species to Critically Endangered in a very short time. For this reason, the species is listed as Vulnerable.

Population justification
Based on opportunistic observations, the population size is suspected to be greater than 500 mature individuals and to possibly number 800-1,000 mature individuals (P. J. McClelland in litt. 2019). However, since the species is secretive and no comprehensive or systematic surveys have been carried out, there is a lot of uncertainty in the population size (P. J. McClelland in litt. 2020). The population comprises at least 200 mature individuals at Campbell Island, 100-200 mature individuals at Whenua Hou/Codfish Island (P. J. McClelland in litt. 2019) and a small population, suspected in 2013 to number fewer than 30 individuals (Williams 2013a), at Dent Island. Individuals occassionally swim the 3 km from Dent Island to Campbell Island.

Trend justification
In 1990, a survey of Dent estimated a population of 60-100 birds (Goudswaard 1991), although other estimates from around the same time estimated just 30 individuals (P. McClelland in litt. 2019). It is likely that no more than 25 breeding pairs were present in 1998 (Gummer and Williams 1999). In 1999-2000, 24 captive-bred birds were released on Whenua Hou/Codfish Island to create a temporary population (Gummer and Williams 1999, Gummer 2006b). The population on Whenua Hou expanded rapidly, with egg-laying occurring in the first year (Williams 2013b). From 2004-2006, 159 birds, including some from Whenua Hou and captive-bred individuals, were reintroduced to Campbell Island (Potter 2006, P. J. McClelland in litt. 2012). The majority of birds released in 2004 were believed to have survived their first year on Campbell Island, and successful breeding was confirmed in 2006 (Anon. 2006). A survey in December 2008 confirmed that the species had established on the island (P. J. McClelland in litt. 2008). This 2008 survey, along with opportunistic observations of breeding and dispersal activity (P. J. McClelland in litt. 2008, 2010, 2011), suggested that the population size in 2012 was between 100 and 200 mature individuals. Based on opportunistic observations, the population size is currently suspected to be greater than 500 mature individuals and to possibly number 800-1,000 mature individuals (P. J. McClelland in litt. 2019). Comprehensive surveys have not been undertaken so population estimates are uncertain, but the population increase is considered to have a high level of certainty, although it may now have stabilised as carrying capacity is reached on the range islands (P. J. McClelland in litt. 2020).


Distribution and population

Anas nesiotis is endemic to New Zealand, where it had been confined to Dent Island, an offshore islet of Campbell Island, for many decades. It was first collected in 1886 from the sea near Campbell (just 3 km away from Dent and likely to have been a stronghold for the species), but was not discovered on Dent until 1975. In 1999-2000, 24 captive-bred birds were released on Whenua Hou/Codfish Island, and egg-laying occurred in their first year (Gummer and Williams 1999, Gummer 2006b). Following the successful eradication of brown rat Rattus norvegicus from Campbell Island, 159 birds, including captive-bred individuals and some taken back from Whenua Hou, were released on Campbell Island between 2004 and 2006 (Potter 2006, P. J. McClelland in litt. 2012). The majority of birds released in 2004 were believed to have survived their first year on Campbell Island, and successful breeding was confirmed in 2006 (Anon 2006). A survey in December 2008 confirmed that the species had established on the island (P. J. McClelland in litt. 2008). On Campbell Island, the species is most recorded around the shoreline, along streams and around pools at Perseverance Harbour, Six-foot Lake, Northeast Harbour and in Northwest Bay (Williams 2013a).

Ecology

The species is flightless. On Campbell Island, it inhabits rocky shorelines, peaty streams and pools in wetlands with profuse sedge and tussock cover (Williams 2013a). Birds have dispersed into open upland areas, Dracophyllum forest, upstream habitats and coastal beaches (Gummer 2006a). It has been observed feeding on tidal flats (Williams 2013a). On Whenua Hou, birds are found throughout the island from coast through to mature forest (P. J. McClelland in litt. 2019). They are regularly found in forest up to a kilometre away from the coast or any significant water courses (P. J. McClelland in litt. 2019). On Dent, where there are no pools or running water, it lives under thick, chest-high tussock. Its diet is unknown in the wild, but in captivity it feeds on amphipods, weevils, earthworms, seaweed and other insects; and it is probably omnivorous with a preference for invertebrates (Williams 2013a). Birds released onto Whenua Hou have been observed feeding on invertebrates in piles of rotting seaweed along the shore and foraging offshore at night (Gummer and Williams 1999). In captivity, females sometimes lay two clutches of between one and four eggs (Preddey 1995). Reintroduced males on Campbell Island hold territories.

Threats

Brown rats Rattus norvegicus on Campbell caused its disappearance from this island (Williams and Robertson 1996, Williams 2013a). The successful eradication of this invasive alien species in 2001 has allowed the species's reintroduction. However, accidental reintroduction of rats, severe weather events, oil spills and the introduction of disease remain possible threats. There is a proposal to reintroduce Brown Teal (Anas chlorotis) to Stewart Island, which is within flying distance of Whenua Hou, and the species was previously found on Whenua Hou. Brown Teal and Campbell Teal would be very likely to hybridise if they had the opportunity (P. J. McClelland in litt. 2019), which could pose a further threat to the species.

Conservation actions

Conservation Actions Underway
The species is listed on CITES Appendix I and is listed as Nationally Vulnerable in New Zealand (Robertson et al. 2017). A recovery plan was produced in 1993 (McClelland 1993).

In 1987, four individuals on Dent Island were taken into captivity at the Pukaha Mount Bruce Wildlife Centre to form a captive breeding programme (Department of Conservation n.d.). The captive population rose to 60 individuals by 2000 (Department of Conservation n.d.) and over a hundred birds were bred for release (P. J. McClelland in litt. 2019). Nearly all have now been released onto Whenua Hou/Codfish Island with only around 20 birds retained as an insurance population (P. J. McClelland in litt. 2008). 

Rattus exulans were removed from Whenua Hou in 1998 (P. J. McClelland in litt. 2019). Rattus norvegicus was successfully eradicated from Campbell Island by 2003 during the world's largest rat eradication programme (BBC 2003, Seddon and Maloney 2003, Gummer 2006b)

In 1999-2000, 24 captive-bred birds were released on Whenua Hou/Codfish Island to create a temporary population (Gummer and Williams 1999, Gummer 2006b). The population on Whenua Hou expanded rapidly, with egg-laying occurring in the first year (Williams 2013b). From 2004-2006, 159 birds, including captive-bred individuals and birds taken from Whenua Hou, were reintroduced to Campbell Island (Potter 2006, P. J. McClelland in litt. 2012). The majority of birds released in 2004 were believed to have survived their first year on Campbell Island, and successful breeding was confirmed in 2006 (Anon 2006). A survey in December 2008 confirmed that the species had established on the island (P. J. McClelland in litt. 2008). All released birds have been screened for disease, but have so far not shown any negative signs (P. J. McClelland in litt. 2008, 2010, 2011). A limited survey of the Campbell population was undertaken in November 2019 which found the population to be healthy and widespread with birds frequently being encountered by visitors to the island (P. J. McClelland in litt. 2019).

Conservation Actions Proposed
Develop a monitoring protocol to monitor the species across all range islands. Monitor population size and trends. Monitor the health of birds in all sub-populations to ensure that they are not suffering from disease. Establish and maintain biocontrol measures and restrict public access to localities where the species occurs to reduce the risk of the introduction of invasive predators (especially R. norvegicus) and disease (McClelland 1993).

 



Identification

48 cm. Small, flightless, dark brown duck. Brown eclipse male, female and juvenile. Mottled dark brown breast. Prominent white eye-patch. Breeding male has glossy green head. Very narrow white collar, flank patch. Voice Soft, high-pitched wheezy whistles and popping (male), low quacks and growls (female).

Acknowledgements

Text account compilers
Wheatley, H.

Contributors
Benstead, P., Bird, J., Butchart, S., Gummer, H., McClellan, R., McClelland, P., Pilgrim, J., Symes, A., Taylor, J., Williams, M. & Young, G.


Recommended citation
BirdLife International (2022) Species factsheet: Anas nesiotis. Downloaded from http://www.birdlife.org on 29/06/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 29/06/2022.