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Sterna dougallii 

Scope: Global
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Charadriiformes Laridae

Scientific Name: Sterna dougallii
Species Authority: Montagu, 1813
Regional Assessments:
Common Name(s):
English Roseate Tern
French Sterne de Dougall
Taxonomic Source(s): Christidis, L. and Boles, W.E. 2008. Systematics and taxonomy of Australian birds. CSIRO Publishing, Collingwood, Australia.
Taxonomic Notes: The BirdLife Taxonomic Working Group is aware that phylogenetic analyses have been published which have proposed generic rearrangements which may affect this species, but prefers to wait until work by other taxonomists reveals how these changes affect the entire groups involved.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2015
Date Assessed: 2012-05-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Facilitator/Compiler(s): Butchart, S., Ekstrom, J., Harding, M., Hatchett, J. & Malpas, L.
Justification:
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Sterna dougallii breeds in widely but sparsely distributed colonies along the east coast and offshore islands of Canada, USA, from Honduras to Venezuela, possibly to Brazil, the Caribbean (including the Bahamas, Greater and Lesser Antilles and the West Indies), UK, France, Ireland, Portugal (Azores, Salvages and perhaps Madeira), Spain (Canary Islands), South Africa, Kenya, Somalia, Madagascar, Oman, Seychelles, St Brandon and the Mascarene Islands (Mauritius), Maldives, Chagos (British Indian Ocean Territory), Andaman and Nicobar Islands (India), Sri Lanka, Ryukyu Islands (Japan), Indonesia, Fiji, Solomon Islands, New Guinea (Papua New Guinea), New Caledonia (to France) and Australia (del Hoyo et al. 1996, Snow and Perrins 1998). This species has a large range, with an estimated global Extent of Occurrence of 1,000,000-10,000,000 km2. It has a large global population estimated to be 78,000-82,000 individuals (Wetlands International 2002). The population in North America underwent a significant decline in 40 years, decreasing from 8,500 pairs in the early 1930s to 2,500 in 1978 (Brown and Nettleship 1984). Numbers, however, appear to have stabilised at 3,000 pairs (del Hoyo et al. 1996). In Nova Scotia, the decline was from 200 to 32 pairs (Brown and Nettleship 1984). Between 1969 and 1992, the UK population declined from 1,018 pairs to 57, and pairs in Ireland dropped from 1,435 to 454 (Sprunt 1984). In 1995, however, over 1,700 pairs bred in Europe. The French population is 100-110 pairs which may be a decline from c.500 in 1973. The large Azores population has fluctuated between 550 and 1,028 pairs from 1989/90 to 1995 (Snow and Perrins 1998). The tropical Indian Ocean may be the most secure region for this species (Feare 1984). The species is threatened by a number of agents of which hunting in the wintering quarters may be the most significant (Buckley and Buckley 1984, Cooper et al. 1984, Avery et al. 1995). Trapping of tern species is still prevalent in Ghana, which has the highest number of wintering S. dougalli of the western African countries (Avery et al. 1995). At the northern European breeding grounds it is not clear which threats are having the most impact. Disturbance and egg-collecting have been stopped in most areas by the use of wardens, but the former still threatens some major colonies in the Azores. Predation by rats, ferrets, red foxes and Peregrine Falcon Falco peregrinus occurs locally, and can have significant effects, including complete breeding failure at some Azores colonies (Avery et al. 1995). Natural predators can often take a great toll on localised colonies, particularly when terns are disturbed from the nest by other birds and humans (Buckley and Buckley 1984, Cooper et al. 1984). Habitat loss in northern Europe is not a major problem but has caused the local extinction of some colonies, as have extreme weather events (Avery et al. 1995). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern.
Countries occurrence:
Native:
Anguilla; Antigua and Barbuda; Aruba; Australia; Bahamas; Belize; Bonaire, Sint Eustatius and Saba (Saba, Sint Eustatius); Brazil; Canada; China; Cuba; Curaçao; Dominica; Dominican Republic; France; Ghana; Grenada; Guadeloupe; Haiti; India; Indonesia; Ireland; Jamaica; Japan; Kenya; Madagascar; Martinique; Mauritius; Mexico; Montserrat; New Caledonia; Oman; Papua New Guinea; Portugal; Puerto Rico; Saint Kitts and Nevis; Saint Lucia; Saint Martin (French part); Saint Vincent and the Grenadines; Seychelles; Sint Maarten (Dutch part); Solomon Islands; Somalia; South Africa; Spain; Sri Lanka; Taiwan, Province of China; Tanzania, United Republic of; Turks and Caicos Islands; United Kingdom; United States; Venezuela, Bolivarian Republic of; Virgin Islands, British; Virgin Islands, U.S.
Vagrant:
Austria; Bahrain; Barbados; Belgium; Bermuda; Brunei Darussalam; Colombia; Denmark; Egypt; Gambia; Germany; Gibraltar; Israel; Libya; Malta; Myanmar; Netherlands; Norway; Poland; Saint Pierre and Miquelon; Saudi Arabia; Singapore; Sweden; Switzerland; Trinidad and Tobago; United Arab Emirates; Vanuatu; Viet Nam; Yemen
Present - origin uncertain:
Benin; Cambodia; Cameroon; Cayman Islands; Christmas Island; Comoros; Côte d'Ivoire; Equatorial Guinea; Fiji; French Guiana; French Southern Territories; Guatemala; Guinea; Guinea-Bissau; Guyana; Iran, Islamic Republic of; Liberia; Malaysia; Mauritania; Mayotte; Micronesia, Federated States of ; Mozambique; Nauru; Nigeria; Norfolk Island; Pakistan; Palau; Panama; Philippines; Réunion; Sao Tomé and Principe; Senegal; Sierra Leone; Suriname; Thailand; Timor-Leste; Togo
Additional data:
Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:765000
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Continuing decline in number of locations:Unknown
Extreme fluctuations in the number of locations:No
Upper elevation limit (metres):18
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The global population is estimated to number c.70,000-82,000 individuals (Wetlands International 2006), while national population estimates include: c.100-10,000 breeding pairs and c.50-1,000 individuals on migration in China; c.100-100,000 breeding pairs and c.50-10,000 individuals on migration in Taiwan and c.100-10,000 breeding pairs and c.50-1,000 individuals on migration in Japan (Brazil 2009).

Trend Justification:  The overall population trend is uncertain, as some populations are decreasing, while others are increasing or stable (Wetlands International 2006).
Current Population Trend:Unknown
Additional data:
Continuing decline of mature individuals:Unknown
Extreme fluctuations:NoPopulation severely fragmented:No
Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:Behaviour The Roseate Tern is a migratory coastal seabird that feeds by plunge diving. It dives from a greater height than other terns. The species breeds in large, dense single- or mixed-species colonies that may contain several thousands of pairs (del Hoyo et al. 1996). It remains gregarious throughout the year, roosting in large groups (Urban et al. 1986, Snow and Perrins 1998) and feeding singly, in small loose groups (Snow and Perrins 1998) or in flocks of many hundreds of individuals (Urban et al. 1986, Snow and Perrins 1998). It is regularly found in mixed species flocks with Lesser Noddy (Anous tenuirostris) and White Tern (Gygis alba) (Ramos 2000). When mixing with the former in conjunction with predatory fish, breeding success was markedly better (Ramos 2000). Large, dense foraging flocks are associated with higher rates of chick feeding (Ramos 2000). Habitat The species nests on sand-dunes, sand-spits, shingle beaches, reefs (Snow and Perrins 1998), saltmarshes and rocky, sandy or coral islands (del Hoyo et al. 1996), showing a preference for densely vegetated sites in temperate regions but sparsely vegetated sites in the tropics (del Hoyo et al. 1996). It also shows a preference for nest sites close to clear, shallow, sandy fishing grounds (Snow and Perrins 1998) in tidal bays and sheltered inshore waters (Snow and Perrins 1998). Throughout the year the species often rests and forages in sheltered estuaries, creeks (Urban et al. 1986), inshore waters and up to several kilometres offshore (del Hoyo et al. 1996), moving to warm tropical coasts after breeding (Snow and Perrins 1998). Diet This species is a specialist forager, and takes a small prey spectrum compared to Common Tern at the same sites (Birdlife International 2000). Its diet consists predominantly of small pelagic fish (Urban et al. 1986, del Hoyo et al. 1996), particularly sandeel (Birdlife International 2000, Newton and Crowe 2000) and sprat (Birdlife International 2000) and sometimes clupeids (Birdlife International 2000, Newton and Crowe 2000)and gadoids (Newton and Crowe 2000), although it will also take insects and marine invertebrates (del Hoyo et al. 1996) such as crustaceans (Urban et al. 1986). Sandeel are particularly important during chick rearing (Newton and Crowe 2000). In Puerto Rico, adult Roseate Terns fed primarily on dwarf herrings (Jenkinsia lamprotaenia) and anchovies (Anchoa spp.), and chicks were mostly fed dwarf herrings and sardines (Harengula and Opisthonema spp.); few anchovies were fed to chicks (Shealer 1998). Breeding site The nest is a bare scrape in sand, shingle or coral rubble (del Hoyo et al. 1996), preferably in sites surrounded by walls and rocks (Newton and Crowe 2000) or in the shelter of vegetation (in temperate regions) (Richards 1990, Snow and Perrins 1998), also in crevices between and under rocks, or in the entrances to rabbit or Puffin burrows (Snow and Perrins 1998). Foraging range At various colonies in New York, USA, birds were observed to forage at sites up to 30 km away from their breeding colony, although at most sites, most birds foraged within 10 km (Birdlife International 2000). Similarly, in Massachusetts, USA, birds foraged at up to 30 km from the breeding colony (Shealer 1996). However, in Puerto Rico birds fed within 2 km of the colony (Shealer 1998). In Ireland, birds at Lady's Island Lake tended to forage about 5 km from the colony at a site 3 km offshore (Newton and Crowe 2000). At Rockabill, Ireland, during chick rearing, birds fed within 10 km of the colony in offshore, relatively deep water (20 - 30 m), but during incubation and post-fledging they appeared to be travelling tens of kilometres to feed over sandbanks to the south (Newton and Crowe 2000). The species may be either coastal or more pelagic in nature, depending on the colony location (Newton and Crowe 2000). Throughout their range they forage in habitats where prey availability is high. Temperate populations feed over tide rips (Birdlife International 2000), shoals (Birdlife International 2000, Environment Canada 2006), inlets (Birdlife International 2000), upwelling areas, and predatory fish that force prey to the surface (Ramos 2000). In Puerto Rico, Roseate Terns feed primarily in deep, open water, and rely heavily on predatory fish to drive prey fish to the surface (Shealer 1998). In the Caribbean, they feed primarily over shoals of predatory fish or along reef margins (Birdlife International 2000). In North American parts of the north-west Atlantic, Roseate Terns appear to use one of two strategies: either foraging over tide-rips, sand shoals and sandbars (Safina 1990, Shealer 1996, Gochfeld et al. 1998), in some cases up to 20-30 km from the colony, or more pelagically in deeper water over schools of predatory fish which flush prey fish species to the surface (Shealer 1996, Gochfeld et al. 1998). Where predatory fish are not relied upon, the birds forage over sandy substrates (Sheer and Kress 1994) in water under 10 m deep (Safina 1990, Sheer and Kress 1994). On Aride Island, Seychelles, birds concentrated their foraging along the coastline exposed to prevailing winds (Ramos 2000).
Systems:Terrestrial; Marine
Continuing decline in area, extent and/or quality of habitat:Unknown
Generation Length (years):10.2
Movement patterns:Full Migrant
Congregatory:Congregatory (and dispersive)

Threats [top]

Major Threat(s): The species is threatened by a number of agents, of which hunting in the wintering quarters may be the most significant (Brown and Nettleship 1984, Buckley and Buckley 1984, Cooper et al. 1984, Avery et al. 1995) (e.g. hunting for food and sport in South America and West Africa) (Avery et al. 1995, del Hoyo et al. 1996, Snow and Perrins 1998). Trapping of tern species is still prevalent in Ghana, which has the highest number of wintering S. dougalli of the western African countries (Avery et al. 1995). At the northern European breeding grounds, the most significant threats are human disturbance (e.g. from habitat development, off-road vehicles and recreation (Buckley and Buckley 1984, van Halewyn and Norton 1984)) and predation from both natural and introduced avian and ground predators (Brown and Nettleship 1984, Buckley and Buckley 1984, Cooper et al. 1984, van Halewyn and Norton 1984, Avery et al. 1995, Snow and Perrins 1998). Disturbance and egg-collecting have been stopped in most areas by the use of wardens, but disturbance still threatens some major colonies in the Azores, whilst egg collecting occurs at some colonies (e.g. in East Africa and the Caribbean) (van Halewyn and Norton 1984, del Hoyo et al. 1996). Predation by rats, ferrets, red foxes and Peregrine Falcon (Falco peregrinus) occurs locally, and can have significant effects, including complete breeding failure at some Azores colonies (Avery et al. 1995). Natural predators can often take a great toll on localised colonies, particularly when terns are disturbed from the nest by other birds and humans (Buckley and Buckley 1984, Cooper et al. 1984). Habitat loss in northern Europe is not a major problem but has caused the local extinction of some colonies, as have extreme weather events (Avery et al. 1995). The species is also vulnerable to pollution and disease (Brown and Nettleship 1984, Avery et al. 1995, Environment Canada 2000).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
Breeding pairs are known to be attracted to coastal locations where artificial nesting sites have been constructed (e.g. beaches of bare shingle and islands or rafts covered with sparse vegetation) (Burgess and Hirons 1992) and nesting-boxes provided (chicks may also use nest-boxes as shelters if adults do not nest in them directly) (Avery et al. 1995, Casey et al. 1995, Newton and Crowe 2000, Environment Canada 2000). Increased breeding successes can also be gained through nest-site vegetation management (Newton and Crowe 2000, Casey et al. 1995), landscaping (e.g. creating terraces or infilling flooded hollows), flood prevention (Newton and Crowe 2000), and continuous wardening to minimise unauthorised disturbance (Newton and Crowe 2000, Casey et al. 1995). Non-lethal predator control (e.g. destroying eggs and nests of gull species attempting to nest on islands) can also be successful in increasing the overall breeding success of the species (Environment Canada 2000, Leonard et al. 2004, Casey et al. 1995).


Citation: BirdLife International. 2015. Sterna dougallii. The IUCN Red List of Threatened Species 2015: e.T22694601A85093166. . Downloaded on 28 September 2016.
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