Data Zone
Justification of Red List category
Although the species has significantly increased in population size as a result of intensive conservation effort, it has an extremely small population comprising fewer than 250 mature individuals that is now thought to be stable, with numbers on one island undergoing a possible long-term decline. As a result, the species is classified as Endangered.
Population justification
In 2014 a minimum of 309 birds were recorded in a census of the population, including about 110 pairs and overall 237 mature individuals (J.E. Dowding in litt. 2016). There were 228 mature individuals in 2019 and the population is considered to be stable (Robertson et al. 2021), therefore is placed in the band 200-249 mature individuals.
Trend justification
As a result of intensive predator management, stock exclusion and nest protection, the population rapidly increased by the mid-2000s to over 300 birds but is estimated to have remained fairly stable since (Moore and Dowding 2017, Robertson et al. 2021). In 1987-1988, the population was estimated at 100-110 birds, including 44 breeding pairs: eight on South East Island (Rangatira), 25 on Chatham Island, nine on Pitt Island and two on Mangere Island. In 1998, a census indicated 140-150 birds, representing a significant increase since 1987-1988. In 2004, a minimum of 266 birds were counted on most of the coast of these four islands in the Chathams group, representing a population of 310-340 birds (Moore 2005, 2007). The population appears to have levelled off as a result of less intensive management, having reached over 100 pairs and 310-360 individuals in total in 2006 (Moore 2008). A minimum of 309 birds were recorded in both 2010 and 2014, including c.110 pairs (Moore and Dowding 2017). The population has slightly decreased from 241 mature individuals in 2010, and 237 in 2014 to 228 in 2019, but is considered stable overall (Robertson et al. 2021). The population on Rangatira (which is not farmed and has no mammalian predators) has declined steadily from about 12 pairs in the 1970s to 2 pairs in 2016, for reasons that are not understood (Moore and Dowding 2017).
Haematopus chathamensis is endemic to the Chatham Islands, New Zealand. In 2010 and 2014, about 85% of the population was on Chatham Island, and 15% on the southern islands (Pitt, South East and Mangere) (J.E. Dowding in litt. 2016). Very small numbers may breed on some smaller islands and stacks.
It builds nests in scrapes on sandy and rocky shores, typically away from the waterline. Occasionally, it nests amongst low vegetation or lines nests with vegetation (F. A. Schmechel in litt. 1999). It lays two to three eggs, usually in a simple scrape in sand or shingle (Moore 2009, Heather and Robertson 2015). It starts breeding from three years old and most pairs attempt breeding each season (98%); productivity is highly variable, depending on year, location, and level of management (Schmechel and Paterson 2005, Moore and Reid 2009). The oldest recorded bird lived for a minimum of 30 years (Moore 2013). It feeds principally on molluscs and marine worms, also taking other invertebrates, by probing and hammering with its bill (Marchant and Higgins 1993, Moore 2009). Bird typically feed on rocky and sandy shores, but on Chatham and Pitt Islands also forage in damp paddocks a short distance inland (Schmechel and Paterson 2005).
On Chatham and Pitt Islands introduced predators (notably feral cats) are the major threat, and nests are occasionally trampled by cattle and sheep (Moore and Reid 2009). Nest loss to storm surges and high tides varies temporally and spatially. In some areas of Chatham Island, pairs may nest close to the tideline because introduced marram grass as a result of farming has reduced open areas further back on the beach (Schmechel and Paterson 2005, Moore et al. 2012). Predation by native birds, especially weka Gallirallus australis, causes some egg losses (Moore and Reid 2009). South East and Mangere Islands are free of mammalian predators, but population sizes are small and variable, and the reason for decline on South East is unknown (Schmechel and O'Connor 1999). On Chatham and Pitt Islands, disturbance by people may affect breeding success (Aikman et al. 2001). Hunting and collecting for museums may have had a significant effect on the species in the past (Dowding and Murphy 2001, Moore 2008). Because the population is small and has been through a bottleneck, it probably has low genetic diversity (J.E. Dowding in litt. 2016).
Conservation Actions Underway
Mangere and South East islands were designated as nature reserves (access requires a permit) in the 1950s. Nest manipulation may have helped to increase hatching success on Chatham; nests are moved slowly back up the beach to mitigate the impacts of flooding. Artificial incubation was trialled but did not increase overall productivity. Stock have been fenced from some beaches on Chatham, with strongly positive results (Moore 2009). Signs have been erected to reduce human and dog disturbance, and marram is being controlled in some areas by replacing it with native vegetation, creating safer nesting environments (Moore and Dowding 2017). Predator control, stock exclusion and re-locating nests away from the high tidemark in northern Chatham Island from 1998-2004 caused productivity to increase from an average of 0.35 to 1.0 chicks per pair per year (Moore and Dowding 2017). Management is currently being carried out at three core sites (Maunganui and Wharekauri on the north coast of Chatham Island, and on the east coast of Pitt Island), but productivity has decreased since 2005 when this became less intensive. Together, these areas hold about 45% of the breeding pairs in the entire population.
Conservation Actions Proposed
Continue research on population dynamics and monitoring of breeding activity. Conduct a full census every 5 years (Moore 2014). Continue cat control and banding/monitoring at the three core managed sites, and continue marram removal in suitable areas. There is some indication that the method of cat control in use (live trapping in cages) has become less effective in recent years and new control techniques are required. Minimise destruction of nests by domestic stock, dogs and people, through communication, education and possibly more fencing (Department of Conservation 2001). Continue to move or raise nests at risk of inundation when possible. Continue habitat management and dune restoration into a wider area (Moore 2014).
48 cm. Black-and-white wader with short, thick legs. Black head, neck, upperparts, upper breast. White underparts with smudgy border on chest. Long, thick red bill. Orange eye-ring. Pink legs. Similar spp. Infrequent straggler Pied Oystercatcher H. longirostris has sharper border between black upperparts and white underparts on lower chest, longer bill, finer legs, feet.
Text account compilers
Vine, J.
Contributors
Dowding, J.E. & Schmechel, F.A.
Recommended citation
BirdLife International (2024) Species factsheet: Chatham Islands Oystercatcher Haematopus chathamensis. Downloaded from
https://datazone.birdlife.org/species/factsheet/chatham-islands-oystercatcher-haematopus-chathamensis on 24/12/2024.
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 24/12/2024.