Sterna dougallii

Taxonomy

Assessment Information

Geographic Range

Habitat and Ecology

Threats

Conservation Actions

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Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	AVES	CHARADRIIFORMES	LARIDAE

Scientific Name:

Sterna dougallii

Species Authority:

Montagu, 1813

Common Name/s:

English	–	Roseate Tern
French	–	Sterne de Dougall

Assessment Information [top]

Red List Category & Criteria:

Least Concern ver 3.1

Year Assessed:

2009

Assessor/s:

BirdLife International

Reviewer/s:

Bird, J., Butchart, S.

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.

History:

2008	–	Least Concern
2004	–	Least Concern
1988	–	Near Threatened

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^{1, 7}. 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 1978². Numbers, however, appear to have stabilised at 3,000 pairs¹. In Nova Scotia, the decline was from 200 to 32 pairs². Between 1969 and 1992, the UK population declined from 1,018 pairs to 57, and pairs in Ireland dropped from 1,435 to 454⁴. 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 1995⁷. The tropical Indian Ocean may be the most secure region for this species⁶. The species is threatened by a number of agents of which hunting in the wintering quarters may be the most significant^{3, 5, 8}. Trapping of tern species is still prevalent in Ghana, which has the highest number of wintering S. dougalli of the western African countries⁸. 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 colonies⁸. Natural predators can often take a great toll on localised colonies, particularly when terns are disturbed from the nest by other birds and humans^{3, 5}. Habitat loss in northern Europe is not a major problem but has caused the local extinction of some colonies, as have extreme weather events⁸. 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:	Native: Anguilla; Antigua and Barbuda; Aruba; Australia; Bahamas; Belize; Brazil; Canada; China; Cuba; Dominica; Dominican Republic; France; Ghana; Grenada; Guadeloupe; Haiti; India; Indonesia; Ireland; Jamaica; Japan; Kenya; Madagascar; Martinique; Mauritius; Mexico; Montserrat; Netherlands Antilles; 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; 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; Virgin Islands, British; Virgin Islands, U.S. Vagrant: Austria; Bahrain; Barbados; Belgium; Bermuda; Brunei Darussalam; Colombia; Denmark; Egypt; Gambia; Germany; Gibraltar; Israel; Libyan Arab Jamahiriya; 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 (the); Guatemala; Guinea; Guinea-Bissau; Guyana; Iran, Islamic Republic of; Liberia; Malaysia; Mauritania; Mayotte; Mozambique; Nauru; Nigeria; Norfolk Island; Pakistan; Palau; Panama; Philippines; Réunion; Sao Tomé and Principe; Senegal; Sierra Leone; Suriname; Thailand; Timor-Leste; Togo
Range Map:	Click here to open the map viewer and explore range.

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 pairs¹. It remains gregarious throughout the year, roosting in large groups^{7, 10} and feeding singly, in small loose groups⁷ or in flocks of many hundreds of individuals^{7, 10}. It is regularly found in mixed species flocks with Lesser Noddy (Anous tenuirostris) and White Tern (Gygis alba)¹⁷. When mixing with the former in conjunction with predatory fish, breeding success was markedly better¹⁷. Large, dense foraging flocks are associated with higher rates of chick feeding¹⁷. Habitat The species nests on sand-dunes, sand-spits, shingle beaches, reefs⁷, saltmarshes and rocky, sandy or coral islands¹, showing a preference for densely vegetated sites in temperate regions but sparsely vegetated sites in the tropics¹. It also shows a preference for nest sites close to clear, shallow, sandy fishing grounds⁷ in tidal bays and sheltered inshore waters⁷. Throughout the year the species often rests and forages in sheltered estuaries, creeks¹⁰, inshore waters and up to several kilometres offshore¹, moving to warm tropical coasts after breeding⁷. Diet This species is a specialist forager, and takes a small prey spectrum compared to Common Tern at the same sites¹⁸. Its diet consists predominantly of small pelagic fish^{1, 10}, particularly sandeel^13,18 and sprat¹⁸ and sometimes clupeids^13,18 and gadoids¹³, although it will also take insects and marine invertebrates¹ such as crustaceans¹⁰. Sandeel are particularly important during chick rearing¹³. 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 chicks¹⁹. Breeding site The nest is a bare scrape in sand, shingle or coral rubble¹, preferably in sites surrounded by walls and rocks¹³ or in the shelter of vegetation (in temperate regions)^{7, 9}, also in crevices between and under rocks, or in the entrances to rabbit or Puffin burrows⁷. 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 km¹⁸. Similarly, in Massachusetts, USA, birds foraged at up to 30 km from the breeding colony²⁰. However, in Puerto Rico birds fed within 2 km of the colony¹⁹. In Ireland, birds at Lady's Island Lake tended to forage about 5 km from the colony at a site 3 km offshore¹³. 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 south¹³. The species may be either coastal or more pelagic in nature, depending on the colony location¹³. Throughout their range they forage in habitats where prey availability is high. Temperate populations feed over tide rips¹⁸, shoals^18,21, inlets¹⁸, upwelling areas, and predatory fish that force prey to the surface¹⁷. In Puerto Rico, Roseate Terns feed primarily in deep, open water, and rely heavily on predatory fish to drive prey fish to the surface¹⁹. In the Caribbean, they feed primarily over shoals of predatory fish or along reef margins¹⁸. 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^20,22,23, 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^20,22. Where predatory fish are not relied upon, the birds forage over sandy substrates²⁴ in water under 10 m deep^23,24. On Aride Island, Seychelles, birds concentrated their foraging along the coastline exposed to prevailing winds¹⁷.
Systems:	Terrestrial; Marine

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 pairs¹. It remains gregarious throughout the year, roosting in large groups^{7, 10} and feeding singly, in small loose groups⁷ or in flocks of many hundreds of individuals^{7, 10}. It is regularly found in mixed species flocks with Lesser Noddy (Anous tenuirostris) and White Tern (Gygis alba)¹⁷. When mixing with the former in conjunction with predatory fish, breeding success was markedly better¹⁷. Large, dense foraging flocks are associated with higher rates of chick feeding¹⁷. Habitat The species nests on sand-dunes, sand-spits, shingle beaches, reefs⁷, saltmarshes and rocky, sandy or coral islands¹, showing a preference for densely vegetated sites in temperate regions but sparsely vegetated sites in the tropics¹. It also shows a preference for nest sites close to clear, shallow, sandy fishing grounds⁷ in tidal bays and sheltered inshore waters⁷. Throughout the year the species often rests and forages in sheltered estuaries, creeks¹⁰, inshore waters and up to several kilometres offshore¹, moving to warm tropical coasts after breeding⁷. Diet This species is a specialist forager, and takes a small prey spectrum compared to Common Tern at the same sites¹⁸. Its diet consists predominantly of small pelagic fish^{1, 10}, particularly sandeel^13,18 and sprat¹⁸ and sometimes clupeids^13,18 and gadoids¹³, although it will also take insects and marine invertebrates¹ such as crustaceans¹⁰. Sandeel are particularly important during chick rearing¹³. 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 chicks¹⁹. Breeding site The nest is a bare scrape in sand, shingle or coral rubble¹, preferably in sites surrounded by walls and rocks¹³ or in the shelter of vegetation (in temperate regions)^{7, 9}, also in crevices between and under rocks, or in the entrances to rabbit or Puffin burrows⁷. 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 km¹⁸. Similarly, in Massachusetts, USA, birds foraged at up to 30 km from the breeding colony²⁰. However, in Puerto Rico birds fed within 2 km of the colony¹⁹. In Ireland, birds at Lady's Island Lake tended to forage about 5 km from the colony at a site 3 km offshore¹³. 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 south¹³. The species may be either coastal or more pelagic in nature, depending on the colony location¹³. Throughout their range they forage in habitats where prey availability is high. Temperate populations feed over tide rips¹⁸, shoals^18,21, inlets¹⁸, upwelling areas, and predatory fish that force prey to the surface¹⁷. In Puerto Rico, Roseate Terns feed primarily in deep, open water, and rely heavily on predatory fish to drive prey fish to the surface¹⁹. In the Caribbean, they feed primarily over shoals of predatory fish or along reef margins¹⁸. 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^20,22,23, 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^20,22. Where predatory fish are not relied upon, the birds forage over sandy substrates²⁴ in water under 10 m deep^23,24. On Aride Island, Seychelles, birds concentrated their foraging along the coastline exposed to prevailing winds¹⁷.

Systems:

Terrestrial; Marine

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^2,3,5,8 (e.g. hunting for food and sport in South America and West Africa)^1,7,8. Trapping of tern species is still prevalent in Ghana, which has the highest number of wintering S. dougalli of the western African countries⁸. At the northern European breeding grounds, the most significant threats are human disturbance (e.g. from habitat development, off-road vehicles and recreation^3,11) and predation from both natural and introduced avian and ground predators^2,3,5,7,8,11. 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)^1,11. 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 colonies⁸. Natural predators can often take a great toll on localised colonies, particularly when terns are disturbed from the nest by other birds and humans^3,5. Habitat loss in northern Europe is not a major problem but has caused the local extinction of some colonies, as have extreme weather events⁸. The species is also vulnerable to pollution and disease^2,8,14.

Major Threat(s):

The species is threatened by a number of agents, of which hunting in the wintering quarters may be the most significant^2,3,5,8 (e.g. hunting for food and sport in South America and West Africa)^1,7,8. Trapping of tern species is still prevalent in Ghana, which has the highest number of wintering S. dougalli of the western African countries⁸. At the northern European breeding grounds, the most significant threats are human disturbance (e.g. from habitat development, off-road vehicles and recreation^3,11) and predation from both natural and introduced avian and ground predators^2,3,5,7,8,11. 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)^1,11. 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 colonies⁸. Natural predators can often take a great toll on localised colonies, particularly when terns are disturbed from the nest by other birds and humans^3,5. Habitat loss in northern Europe is not a major problem but has caused the local extinction of some colonies, as have extreme weather events⁸. The species is also vulnerable to pollution and disease^2,8,14.

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)¹² and nesting-boxes provided (chicks may also use nest-boxes as shelters if adults do not nest in them directly)^8,16,13,14. Increased breeding successes can also be gained through nest-site vegetation management^13,16, landscaping (e.g. creating terraces or infilling flooded hollows), flood prevention¹³, and continuous wardening to minimise unauthorised disturbance^13,16. 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^14,15,16. Conservation Actions Proposed

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)¹² and nesting-boxes provided (chicks may also use nest-boxes as shelters if adults do not nest in them directly)^8,16,13,14. Increased breeding successes can also be gained through nest-site vegetation management^13,16, landscaping (e.g. creating terraces or infilling flooded hollows), flood prevention¹³, and continuous wardening to minimise unauthorised disturbance^13,16. 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^14,15,16.

Conservation Actions Proposed

Citation:	BirdLife International 2009. Sterna dougallii. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 08 February 2012.
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