Data Zone
Justification of Red List category
Although this species' population size is thought to be increasing owing to ongoing translocations to predator-free islands, it has an extremely small population of less than 250 mature individuals and a very restricted range. It is therefore classified as Endangered.
Population justification
In 2021/22, the total wild breeding population numbered about 85 pairs. About 55% of the breeding pairs were on South East Island, and 36% on Waikawa/Portland Island (J. E. Dowding in litt. 2022). These are the only populations that can currently be considered relatively secure and self-sustaining in the long term.
Trend justification
The species' population is now thought to be increasing as reintroductions increase the number of breeding subpopulations on predator free islands (Robertson et al. 2021). Numbers on South East and Mangere Islands are currently stable, and both populations are at carrying capacity. There are currently no pairs breeding on Motutapu Island. The recent increase in the total number of pairs has been entirely the result of the recovery of the population on Waikawa/Portland Island (J.E. Dowding in litt. 2022).
Thinornis novaeseelandiae breeds on South East Island (Rangatira) (with vagrants to Pitt Island) in the Chatham Islands, New Zealand. A small population on Western Reef, Chatham Islands declined following its discovery in 1999, when 21 individuals were known (Bell and Bell 2000), and the last individual was taken into captivity in 2003 (Dowding et al. 2005). The species was once occurred around the coast of at least the South Island, but was probably never common. It had almost certainly been extirpated from mainland New Zealand by the 1870s. In 1937, the population on South East Island was estimated at 72 pairs (Fleming 1939). Since grazing ceased there in the 1960s, inland pasture used for nesting has become overgrown, and the population has declined and become largely restricted to the coast (Department of Conservation 2001). It has stabilised at 44-48 pairs and a post-breeding total in recent years of 115-150 adults (J.E. Dowding in litt. 2022). A population was re-established on Mangere Island, Chatham Islands by transfer of juveniles from South East Island between 2001 and 2003 (Dowding and O’Connor 2013). Suitable habitat is limiting on Mangere Island, and that population has stabilised at 6-8 pairs. Releases of captive-bred birds on islands off mainland New Zealand have had mixed success. On Motuora Island, Hauraki Gulf, two pairs bred but a population failed to establish and the two remaining males were re-captured for use in the captive-breeding programme (Dowding and O’Connor 2013). Translocations of juveniles to Waikawa/Portland Island from 1998 resulted in the establishment of a population that had reached 37 breeding pairs by 2011 (Dowding and O’Connor 2013)). A rat incursion (probably a single Norway rat) in 2012 reduced this population to 4 pairs, but it has rebuilt (with further releases), and 31 pairs bred in 2021/22 (J.E. Dowding in litt. 2022). In 2006, a single release was made at Release Site 4, an island off the South Island; further releases there were halted when birds were found to be carrying avian pox, and a population did not establish. In 2007, releases began on Mana Island, near Wellington. That population had reached 10 pairs by 2010/11, but an incursion by a single Norway rat in mid-2011 (Dowding and O’Connor 2013) eventually resulted in its extirpation (J.E. Dowding in litt. 2016). Further releases on Mana Island have failed due to avian predation and high levels of dispersal, and it has now been abandoned as a release site (J.E. Dowding in litt. 2022). Releases have also occurred on Motutapu Island since 2012, but adult survival in that population has been much lower than at other sites, probably due to avian predation. Analysis of demographic data from 2012-2019 shows that under current conditions a self-sustaining population cannot be established there. There have also been several stoat incursions on Motutapu since 2020, as a result of which some birds were killed, and others were returned to captivity to prevent further losses (J.E. Dowding in litt. 2022).
On South East Island, it nests at the head of rock wave-platforms, and on salt meadow (J. E. Dowding in litt. 2008). While most birds on South East and Mangere Islands are confined to tidal rock platforms (there are no sandy beaches or estuaries), birds released on islands around the New Zealand mainland have used a wide range of habitat types, including sandy beaches, rocky shorelines, shingle beaches, and tidal estuaries (Dowding 2013, Dowding and O'Connor 2013). It feeds on small crustaceans, molluscs and other invertebrates, using the “run/step-stop-peck” technique typical of plovers, as well as "foot-trembling and beak probing" behaviour (Marchant and Higgins 1993, Armitage 2008). It lays two to three eggs in a nest set under dense vegetation, beach rack or boulders, usually on or near the shoreline (Davis 1994, Heather and Robertson 1997). On South East Island, where the population is at carrying capacity, breeding usually begins in the second or third year. Breeding has occurred in the first year at reintroduction sites and in captivity, where resources are less limiting (Dowding and O'Connor 2013). In the period 1986-1993, the average age of the population on South East Island was about six years (Dowding and Kennedy 1993, Davis 1994). The oldest known individual was a male aged 21 years (J. E. Dowding in litt. 2008).
Cats and brown rats Rattus norvegicus were probably the immediate cause of its extirpation from the South Island (Dowding and Kennedy 1993, Davis 1994) and cats reduced its range further on the Chatham Islands in the late 19th century (Dowding and Murphy 2001). The removal of sheep from South East Island in 1961 has resulted in loss of breeding habitat as previously grazed pasture used for nesting (Fleming 1939) has become overgrown. A small part of the marsh-turf near the south coast has also become overgrown; this process is likely to continue slowly but is not considered a serious concern. Other threats include fire, expansion of fur seal Arctocephalus forsteri colonies, disease, rough seas and storms, human disturbance and predation by Brown Skuas Catharacta antarctica (J. E. Dowding in litt. 1999, Department of Conservation 2001). Island visitors heighten these threats (Department of Conservation 2001). Losses from translocated populations have largely been the result of dispersal by juveniles to the mainland (where they are killed by predators, although some birds have survived for several years before vanishing) and predation at the release sites by native avian predators, including Morepork Ninox novaeseelandiae (Aikman 1999), New Zealand falcon Falco novaeseelandiae, Kelp Gull Larus dominicanus, and Swamp Harrier Circus approximans (Dowding and O’Connor 2013). Rat incursions on Waikawa/Portland and Mana Islands have demonstrated the extreme susceptibility of this species to introduced mammalian predators. The arrival of cats, rats, or mustelids (stoats, weasels or ferrets) is a constant threat requiring stringent biosecurity at all shore plover sites. These pests are common on mainland New Zealand. Outbreaks of avian pox in the captive population have caused mortality and delays in releases (Dowding and O’Connor 2013).
Conservation Actions Underway
The recovery programme is overseen by the Department of Conservation’s Shore Plover Recovery Group. Birds are captive-bred at three institutions and the juveniles produced are released on suitable predator-free islands around mainland New Zealand. In 2019 the recovery programme had produced a record of 46 chicks (Ornithological Society of New Zealand 2019). The incursions on Waikawa/Portland and Mana Islands (both believed to be of a single Norway rat) have demonstrated the extreme susceptibility of shore plover to mammalian predators larger than mice. Quarantine and surveillance measures are in place at all sites with shore plover to prevent the introduction of rats, cats, and mustelids. All populations are monitored at least twice annually. The recovery plan for the species has expired, and a new plan is nearing completion
Conservation Actions Proposed
Continue the captive-breeding and release programme at suitable sites around mainland New Zealand. Genetic diversity in the captive population was low, and further eggs were taken from South East Island in 2020. Progeny from these eggs will be released into existing populations on islands around the mainland to increase diversity (J.E. Dowding in litt. 2022). Further releases are to occur on Motutapu Island and experimental removal of some avian predators is planned there to see whether this improves adult survival (J.E. Dowding in litt. 2022). A proposal to remove cats from Pitt Island, with a view to increasing the potential range of the species on the Chatham Islands, is under discussion (J.E. Dowding in litt. 2022).
20 cm. Stocky plover. Adult male, black forehead, sides of face, throat, collar. Brown in female. White ring above forehead, around back of head. Grey-brown crown, back of head, upper body. White underparts. Orange-red bill with black tip. Orange legs. Juvenile, white head, neck. Brown-grey cap, eye-patch. Brown bill with orange base. Voice Usual call kleet, adults call rapidly like oystercatchers when aggressive.
Text account compilers
Taylor, J., Vine, J., Stringer, C., Harding, M., Khwaja, N., Benstead, P., McClellan, R., Mahood, S., Butchart, S.
Contributors
Aikman, H., Askew, N., Dowding, J.E., Hitchmough, R., Miskelly, C., O'Connor, S. & Szabo, M.
Recommended citation
BirdLife International (2024) Species factsheet: Shore Plover Thinornis novaeseelandiae. Downloaded from
https://datazone.birdlife.org/species/factsheet/shore-plover-thinornis-novaeseelandiae on 22/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 22/12/2024.