Charadrius sanctaehelenae

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

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Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	AVES	CHARADRIIFORMES	CHARADRIIDAE

Scientific Name:

Charadrius sanctaehelenae

Species Authority:

(Harting, 1873)

Common Name/s:

English

–

Saint Helena Plover, St Helena Plover, St. Helena Plover, Wirebird

Assessment Information [top]

Red List Category & Criteria:

Critically Endangered C2a(ii) ver 3.1

Year Published:

2010

Assessor/s:

BirdLife International

Reviewer/s:

Calvert, R., Symes, A., Butchart, S.

Contributor/s:

Burns, F., Prater, T., McCulloch, N., Sanders, S., Rowlands, B., Duff, E., Roberts, J.

Justification:
This species is classified as Critically Endangered because its extremely small population has declined within the last three generations owing to land-use change (particularly a decrease in grazing pressure) and predation by invasive predators. The population has recently shown some signs of recovery however, and if it remains above 250 mature individuals for a five year period until 2011 it is likely to be eligible for downlisting.

History:

2009	–	Critically Endangered
2008	–	Critically Endangered
2007	–	Critically Endangered
2004	–	Vulnerable
2000	–	Endangered
1996	–	Endangered
1994	–	Endangered

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 1970s⁸. 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^4,11, but survey data from 2005 and 2006 showed further evidence of a decline with an estimated 200-220 mature individuals¹⁴. Full January surveys in 2007-2010 located between 397 and 297 (averaging 353) adults^15,18, with 350 recorded in 2011²². This indicates that a population increase has occurred and some recovery has taken place¹⁵, however the cause of these apparent fluctuations is still unclear.
Countries:	Native: Saint Helena
Range Map:	Click here to open the map viewer and explore range.

Population [top]

Population:	The population has been estimated at 200-220 mature individuals (McCulloch 2006; T. Prater in litt. 2006). However, surveys in 2008 and 2010 found 373 and 397 mature individuals respectively, and the population also exceeded 250 mature individuals in 2007 (F. Burns in litt. 2008). Therefore, although a population estimate of 50-249 mature individuals is precautionarily retained here, if the number of mature individuals remains above this threshold over the five year period 2007-2011 it is likely to qualify for downlisting.
Population Trend:	Decreasing

Population:

The population has been estimated at 200-220 mature individuals (McCulloch 2006; T. Prater in litt. 2006). However, surveys in 2008 and 2010 found 373 and 397 mature individuals respectively, and the population also exceeded 250 mature individuals in 2007 (F. Burns in litt. 2008). Therefore, although a population estimate of 50-249 mature individuals is precautionarily retained here, if the number of mature individuals remains above this threshold over the five year period 2007-2011 it is likely to qualify for downlisting.

Population Trend:

Decreasing

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^1,2. Some populations occupy semi-desert habitats¹⁷. Extended rain seasons resulting in extensive vegetation growth can delay or prevent breeding¹¹. 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: 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 flocks¹.
Systems:	Terrestrial

Habitat and Ecology:

Some 70% of its population occurs in pastureland, with highest densities in relatively dry, flat, short-sward pastures^1,2. Some populations occupy semi-desert habitats¹⁷. Extended rain seasons resulting in extensive vegetation growth can delay or prevent breeding¹¹. 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: 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 flocks¹.

Systems:

Terrestrial

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 cattle (sheep at two sites) densities, and reductions in arable land may have resulted in a decline in the quality of feeding and nesting habitat at some sites^3,5. For the same reason, scrub encroachment has resulted in a major population decline at one site⁵, and the spread of invasive plant species has further altered habitats on the island¹⁶. These factors probably resulted in the significant declines of the early 1990s^11,12. In addition, invertebrate prey populations may be subject to large-scale, short-term fluctuations⁴. Cats, rats (mostly Rattus norvegicus) and, to a lesser extent, Common Myna Acridotheres tristis are probably significant predators of chicks and nests respectively^2,4. Using motion sensitive, infra-red cameras situated near to nests, cats, rats, Common Myna and sheep have been shown to predator and disturb eggs, and nest survival rates have been found to range from 6-47% due to variation in predation levels¹⁵. Evidence suggests feral cat populations may be increasing. Less effort has gone into trapping feral cats or neutering domestic pets in recent years¹³. However, successful cat control may lead to an increase in the rat population, through decrease predation and increased food availability¹⁵. 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 2010¹⁹; however, the current plans are not thought to pose a serious threat to the species²⁰. There is concern, however, over the potential for poorly-planned and inappropriate tourist developments²⁰.

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 cattle (sheep at two sites) densities, and reductions in arable land may have resulted in a decline in the quality of feeding and nesting habitat at some sites^3,5. For the same reason, scrub encroachment has resulted in a major population decline at one site⁵, and the spread of invasive plant species has further altered habitats on the island¹⁶. These factors probably resulted in the significant declines of the early 1990s^11,12. In addition, invertebrate prey populations may be subject to large-scale, short-term fluctuations⁴. Cats, rats (mostly Rattus norvegicus) and, to a lesser extent, Common Myna Acridotheres tristis are probably significant predators of chicks and nests respectively^2,4. Using motion sensitive, infra-red cameras situated near to nests, cats, rats, Common Myna and sheep have been shown to predator and disturb eggs, and nest survival rates have been found to range from 6-47% due to variation in predation levels¹⁵. Evidence suggests feral cat populations may be increasing. Less effort has gone into trapping feral cats or neutering domestic pets in recent years¹³. However, successful cat control may lead to an increase in the rat population, through decrease predation and increased food availability¹⁵. 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 2010¹⁹; however, the current plans are not thought to pose a serious threat to the species²⁰. There is concern, however, over the potential for poorly-planned and inappropriate tourist developments²⁰.

Conservation Actions [top]

Conservation Actions:	Conservation Actions Underway All bird species on St Helena have been protected by law since 1894⁶. The St Helena National Trust (SHNT) has been formed to coordinate the work of environmental NGOs⁷, including population monitoring, ecological research, habitat restoration and raising public awareness^3,10. Over 150 ha of pastures have been enhanced for the species²¹. A programme of trapping appears to have formerly reduced feral cat populations in some areas³but has recently become irregular¹⁴ and neutering of domestic pets is now infrequent. New predator control programmes were due to be initiated in early 2011²². 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 grant¹⁵. 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 Vulnerable¹⁶. A PhD studentship based at the University of Bath, which began in October 2007, investigated the conservation biology of the St Helena Plover¹⁴. As part of this project nest exclosures, designed to prevent predation of eggs by cats, are being trialled at present¹⁵. Conservation Actions Proposed Monitor populations regularly, increase research into the effects of pasture management and introduced species^1,2,9,15. Maintain pastures as grazing land and manage appropriately⁴. Monitor changes in habitat quality closely. Restrict vehicle access to significant semi-desert sites³. Ensure that mitigation measures are in place for the proposed airport at Prosperous Bay Plain. Intensify trapping of feral cats and the killing of rats around known sites. Closely monitor development plans for the airport and tourist infrastructure²⁰.

Conservation Actions:

Conservation Actions Underway
All bird species on St Helena have been protected by law since 1894⁶. The St Helena National Trust (SHNT) has been formed to coordinate the work of environmental NGOs⁷, including population monitoring, ecological research, habitat restoration and raising public awareness^3,10. Over 150 ha of pastures have been enhanced for the species²¹. A programme of trapping appears to have formerly reduced feral cat populations in some areas³but has recently become irregular¹⁴ and neutering of domestic pets is now infrequent. New predator control programmes were due to be initiated in early 2011²². 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 grant¹⁵. 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 Vulnerable¹⁶. A PhD studentship based at the University of Bath, which began in October 2007, investigated the conservation biology of the St Helena Plover¹⁴. As part of this project nest exclosures, designed to prevent predation of eggs by cats, are being trialled at present¹⁵.

Conservation Actions Proposed
Monitor populations regularly, increase research into the effects of pasture management and introduced species^1,2,9,15. Maintain pastures as grazing land and manage appropriately⁴. Monitor changes in habitat quality closely. Restrict vehicle access to significant semi-desert sites³. Ensure that mitigation measures are in place for the proposed airport at Prosperous Bay Plain. Intensify trapping of feral cats and the killing of rats around known sites. Closely monitor development plans for the airport and tourist infrastructure²⁰.

Citation:	BirdLife International 2010. Charadrius sanctaehelenae. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 26 May 2012.
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