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Charadrius sanctaehelenae 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Charadriiformes Charadriidae

Scientific Name: Charadrius sanctaehelenae (Harting, 1873)
Common Name(s):
English St Helena Plover, Saint Helena Plover, St. Helena Plover, Wirebird
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
Identification information: 15 cm. Long-legged, buffy plover. Very similar to Kittlitz's Plover C. pecuarius, but is larger, has longer and thinner legs and longer bill. Black head markings do not meet on the nape and underparts are less buffy. Immature lacks head markings and is generally duller version of adult with paler underparts. Voice Soft and short, kee-vit notes. Hints Best seen at Deadwood and Prosperous Bay Plains and Woody Ridge.

Assessment Information [top]

Red List Category & Criteria: Vulnerable D1 ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Burns, F., Cairns-Wicks, R., Duff, E., George, K., Hall, J., Hillman, C., Hoffman, D., McCulloch, N., Millett, J., Oppel, S., Prater, T., Roberts, J., Rowlands, B., Sanders, S., Stowe, T., Vickery, J., Leo, D. & Harris, J.
Facilitator/Compiler(s): Benstead, P., Bird, J., Butchart, S., Calvert, R., Ekstrom, J., Mahood, S., Pilgrim, J., Symes, A., Taylor, J., Ashpole, J, Stringer, C., Westrip, J.
Justification:

This species was classified as Critically Endangered because until very recently its population was extremely small and declining owing to land-use change (particularly a decrease in grazing pressure) and predation by invasive predators. Since 2005 surveys have shown a stable or increasing population, which has remained higher than 250 mature individuals since at least 2007 owing to successful management. Consequently this species has now been downlisted to Vulnerable. Given uncertainty over the impacts of the new airport, the status of this species should continue to be monitored closely.

Previously published Red List assessments:

Geographic Range [top]

Range Description:This species is the only surviving endemic landbird on St Helena (to UK) and may have declined sharply in the 1970s (Rowlands et al. 1998). Surveys in 1988-1989 (giving a total of c. 450 individuals), repeated in 1998-1999, revealed large declines at all important pastureland sites, and were not compensated by concurrent increases in lower density populations at semi-desert sites. Fieldwork in 1999-2000 and 2000-2001 suggested populations had stabilised at c.350 adults (N. McCulloch in litt. 2000, N. McCulloch in litt. 2003), but survey data from 2005 and 2006 showed further evidence of a decline with an estimated 200-220 mature individuals (N. McCulloch in litt. 2007). Full January surveys in 2007-2010 located between 397 and 297 (averaging 353) adults (F. Burns in litt. 2008, 2010, Ellick et al. in litt. 2010), with 350 recorded in 2011 (E. Duff in litt. 2011). This indicates that a population increase has occurred and some recovery has taken place (F. Burns in litt. 2008, 2010); however, the cause of these apparent fluctuations is still unclear.

Countries occurrence:
Native:
Saint Helena, Ascension and Tristan da Cunha (Saint Helena (main island))
Additional data:
Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:70
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:11-100Continuing decline in number of locations:Yes
Extreme fluctuations in the number of locations:NoLower elevation limit (metres):160
Upper elevation limit (metres):680
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The population was previously estimated at 200-220 mature individuals (T. Prater in litt. 2006). However, surveys in 2008, 2010 and 2015 found 373, 397 and >400 mature individuals respectively (Anon. 2015), and the population also exceeded 250 mature individuals in 2007 (F. Burns in litt. 2008). It is now considered that the population has exceeded 250 mature individuals since at least 2007, with the most recent count in 2016 recording 559 mature individuals (Oppel in litt. 2015, Fisher 2016).

Trend Justification:  Surveys in 1988-1989 (giving a total of c. 450 individuals), repeated in 1998-1999, revealed large declines at all-important pastureland sites. Fieldwork in 1999-2000 and 2000-2001 suggested populations had stabilised at c. 350 adults, but survey data from 2005 and 2006 showed further evidence of a decline with an estimated 200-220 mature individuals. A full survey in 2008 located 373 adults, an increase of 16% from 2007, and there was a further population increase to 397 adults in 2010, indicating that some recovery has taken place (F. Burns in litt. 2008, Ellick et al. in litt. 2010), although only 350 adults were counted in 2011 (E. Duff in litt. 2011). The cause of these apparent fluctuations is still unclear. An overall decline of 20-29% is estimated to have occurred within the last 16 years or three generations.

Current Population Trend:Increasing
Additional data:
Number of mature individuals:560Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
No. of subpopulations:1Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:Yes
No. of individuals in largest subpopulation:100

Habitat and Ecology [top]

Habitat and Ecology:Some 70% of its population occurs in pastureland, with highest densities in relatively dry, flat, short-sward pastures (McCulloch 1992, 1999). Some populations occupy semi-desert habitats (McCulloch 2009). Extended rain seasons resulting in extensive vegetation growth can delay or prevent breeding (N. McCulloch in litt. 2003). It feeds on a wide range of invertebrates. More than one clutch (of two eggs) may be laid each year and replaced if eggs or chicks are lost (Burns et al. 2013a): the proportion of a clutch that survives to independence is probably less than 20%, although adult survival is most likely high. Juveniles disperse widely in small flocks (McCulloch 1992).

Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):5.2
Movement patterns:Not a Migrant
Congregatory:Congregatory (and dispersive)

Threats [top]

Major Threat(s): Livestock grazing has become unprofitable over much of St Helena, leading to major alterations to its preferred short-sward grassland habitat. Sward growth, due to lowered densities of cattle (and sheep at two sites), and reductions in arable land may have resulted in a decline in the quality of feeding and nesting habitat at some sites (Norris and McCulloch 1999, N. McCulloch in litt. 1999). For the same reason, scrub encroachment has resulted in a major population decline at one site (Norris and McCulloch 1999), and the spread of invasive plant species has further altered habitats on the island (RSPB undated). These factors probably resulted in the significant declines of the early 1990s (McCulloch and Norris 2001, N. McCulloch in litt. 2003). In addition, invertebrate prey populations may be subject to large-scale, short-term fluctuations (N. McCulloch in litt. 2000). Predation has been shown to be the primary cause of nest failure (Burns et al. 2013a). Cats, rats (mostly Rattus norvegicus) and, to a lesser extent, Common Mynas Acridotheres tristis are known predators of chicks and nests. Using motion sensitive, infra-red cameras situated near to nests, cats, rats, Common Mynas and sheep have been shown to predate and disturb eggs, and nest survival rates have been found to range from 6 to 47% due to variation in predation levels (F. Burns in litt. 2008, 2010, Burns et al. 2013a). Cats have been shown to predate the largest proportion of nests, being responsible for 65% of predated nests monitored during a study in 2007-2008, followed by rats (15%) and Common Mynas (10%) (Burns et al. 2013a). Evidence suggests feral cat populations may be increasing. Less effort has gone into trapping feral cats or neutering domestic pets in recent years (McCulloch 2006). However, successful cat control may lead to an increase in the rat population, through decreased predation and increased food availability (F. Burns in litt. 2008, 2010, Burns et al. 2013a). Rabbits are also becoming a problem as their abundance is destroying the nesting grounds (D. Leo in litt. 2016). In addition to the mammalian and avian predators, the non-native, big-headed ant Pheidole megacephala, was observed swamping a small number of  nests in 2007-2008 and represents a potential threat (Burns et al. 2013a).

Increasing recreational use of off-road vehicles in semi-desert areas may result in disturbance and nest-destruction. Housing development has recently encroached on a number of minor breeding locations. Stalled plans to develop an airport on St Helena were reinstated in 2010 (UKPA 2010). There is considerable uncertainty over the extent and location of developments associated with the airport and the anticipated increase in tourism, the extent of future mitigation measures, and the threat posed by the introduction of invasive species (T. Prater et al. in litt. 2011). The airport is being built on one of the species's breeding sites in the semi-desert of Prosperous Bay. Associated developments are to include additional housing, roads, hotels and a golf course. New housing developments adjacent to important sites for the species may lead to increasing predation of nests by domestic animals, particularly cats. Similarly, a proposed new garbage transfer station may attract potential nest predators like rats and cats. To compensate for the expected impacts on the species, a large mitigation project has been in place since 2008. This project aimed to improve habitat in several of the species's pastureland breeding sites by removing scrub and increasing grazing intensity. This work has been successful in creating suitable breeding habitat in grassland, but the extent to which it will actually compensate for the development is unclear, as there is uncertainty of future funding, the project has focussed on dry grassland rather than the semi-desert habitat that will be affected by the airport, and success so far in increasing numbers locally has been limited. The ability of breeding pairs to relocate is currently unknown. Off-road driving with all-terrain vehicles is expected to increase with increases in the residential population and tourism. The import of construction material and engineering equipment, and the potentially large increase in visitors, may lead to the inadvertent introduction of other non-native species. The most important breeding site (Deadwood Plain), with 20% of the breeding population, has been ear-marked for a significant wind turbine development, with apparently no proposed mitigation measures (T. Prater et al. in litt. 2011).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
All bird species on St Helena have been protected by law since 1894 (Pitman 1965). The St Helena National Trust (SHNT) has been formed to coordinate the work of environmental NGOs (Rowe 1998), including population monitoring, ecological research, habitat restoration and raising public awareness (Smith 1997, N. McCulloch in litt. 1999), and it remains committed to the wirebird in its 2015-2020 strategy (J. Harris in litt. 2016). Over 150 ha of pastures have been enhanced for the species (J. Roberts in litt. 2010). A programme of trapping appears to have formerly reduced feral cat populations in some areas (N. McCulloch in litt. 1999) but has recently become irregular (N. McCulloch in litt. 2007) and neutering of domestic pets is now infrequent. New predator control programmes were due to be initiated in early 2011 (E. Duff in litt. 2011). The Royal Society for the Protection of Birds, The Agriculture and Natural Resource Department and the SHNT are currently operating a project titled "St Helena Airport and supporting infrastructure: Mitigation for the Impacts on the Wirebird population" through a Department for International Development grant (F. Burns in litt. 2008, 2010). A Species Action Plan was launched in January 2008 with a ten-year goal that the species should have a stable, relatively large population which does not need continuous conservation intervention, such that it can be downlisted to Vulnerable (RSPB undated). A PhD studentship based at the University of Bath, which began in October 2007, investigated the conservation biology of the St Helena Plover (N. McCulloch in litt. 2007). As part of this project nest exclosures, designed to prevent predation of eggs by cats, were trialled (F. Burns in litt. 2008, 2010). The results of these trials showed that exclosures were not a suitable conservation measure for the species: clutch survival was similar between nests with and without predator exclosure cages, and exclosures may have increased adult mortality (Burns et al. 2013b).

Conservation Actions Proposed
Continue to closely monitor the population on a regular basis. Increase research into the effects of pasture management and control of introduced species (McCulloch 1992, 1999, B. Rowlands in litt. 1999, F. Burns in litt. 2008, 2010). Maintain pastures as grazing land and manage appropriately (N. McCulloch in litt. 2000). Monitor changes in habitat quality closely. Restrict vehicle access to significant semi-desert sites (N. McCulloch in litt. 1999). Ensure that mitigation measures are introduced for the airport currently under construction at Prosperous Bay Plain. Intensify the control of feral cats and rats around known breeding sites. Closely monitor development plans for the airport and tourist infrastructure (N. McCulloch in litt. 2010, T. Prater et al. in litt. 2011).


Citation: BirdLife International. 2016. Charadrius sanctaehelenae. The IUCN Red List of Threatened Species 2016: e.T22693785A93423145. . Downloaded on 23 September 2017.
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