EN
Chatham Oystercatcher Haematopus chathamensis



Justification

Justification of Red List Category
This species is listed as Endangered because it has an extremely small population. It has significantly increased over the last 20 years, probably owing to intensive conservation efforts. However, even on islands free from mammalian predators, population sizes fluctuate, with numbers on one island undergoing a possible long-term decline.

Population justification

In 2014, a minimum of 309 birds included 237 mature individuals (J.E. Dowding, in litt. 2016). The population is therefore placed in the band 50-249 mature individuals.


Trend justification
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 four islands in the Chathams group, representing a population of 310-340 birds (Moore 2005, 2007). The population appears to have levelled off, having reached over 100 pairs and 310-360 individuals in total in 2006 (Moore 2008). The population, therefore, is estimated to have remained fairly stable over the last 10 years, having increased very rapidly in the 10 preceding years.

Distribution and population

Haematopus chathamensis is endemic to the Chatham Islands, New Zealand. 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. Numbers on South East, however, appear to have gradually declined since the 1970s (Schmechel and O'Connor 1999) and a slow decline continues (J.E. Dowding in litt. 2016). Very small numbers may breed some smaller islands and stacks. In 2004, a minimum of 266 birds were counted on most of the coast of four islands in the Chathams group, representing a population of 310-340 birds, including 89 pairs (Moore 2008). Censuses in 2006, 2010 and 2014 suggest the population has levelled off at 110-120 pairs, and about 300-320 individuals (J.E. Dowding in litt. 2016). 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).


Ecology

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 (Heather and Robertson 2015, Moore 2009). 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).



Threats

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 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

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. Recently, intensive predator control combined with nest manipulation between 1998 and 2004 resulted in high annual productivity and a sharp rise in the total population. Less intensive 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). Together, these areas hold about 45% of the breeding pairs in the entire population. 

Conservation Actions Proposed
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). Move or raise nests at risk of inundation when possible. Undertake periodic censuses of the whole population (Moore 2009). The recovery plan for the species expired in 2011 and a new plan is required.

Identification

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.

Acknowledgements

Text account compilers
Pilgrim, J., Khwaja, N., Taylor, J., Benstead, P., McClellan, R., Mahood, S., Stringer, C.

Contributors
Dowding, J., Aikman, H., Sawyer, S., Taylor, G.A., Bell, B., Schmechel, F.


Recommended citation
BirdLife International (2020) Species factsheet: Haematopus chathamensis. Downloaded from http://www.birdlife.org on 03/04/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 03/04/2020.