Onychoprion fuscatus 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Charadriiformes Laridae

Scientific Name: Onychoprion fuscatus (Linnaeus, 1766)
Common Name(s):
English Sooty Tern
French Sterne fuligineuse
Onychoprion fuscata ssp. fuscata — Christidis and Boles (2008)
Onychoprion fuscatus — AOU checklist (1998 + supplements)
Sterna fuscata Linnaeus, 1766
Taxonomic Source(s): Cramp, S. and Simmons, K.E.L. (eds). 1977-1994. Handbook of the birds of Europe, the Middle East and Africa. The birds of the western Palearctic. Oxford University Press, Oxford.
Taxonomic Notes: Onychoprion fuscatus (del Hoyo and Collar 2014) was previously placed in the genus Sterna as S. fuscata.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2017
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Dowsett, R.J.
Facilitator/Compiler(s): Butchart, S., Calvert, R., Ekstrom, J., Malpas, L.
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 extremely 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:The Sooty Tern breeds on tropical islands and ranges through most of the tropical oceans (del Hoyo et al. 1996).
Countries occurrence:
American Samoa; Anguilla; Antigua and Barbuda; Argentina; Aruba; Australia; Bahamas; Barbados; Belize; Bermuda; Bonaire, Sint Eustatius and Saba (Saba, Sint Eustatius); Brazil; British Indian Ocean Territory; Cameroon; Canada; Cayman Islands; Chile; China; Cocos (Keeling) Islands; Colombia; Comoros; Cook Islands; Costa Rica; Cuba; Curaçao; Djibouti; Dominica; Dominican Republic; Ecuador; El Salvador; Equatorial Guinea; Fiji; French Guiana; French Polynesia; French Southern Territories; Grenada; Guadeloupe; Guam; Guatemala; Guyana; Haiti; Honduras; India; Indonesia; Iran, Islamic Republic of; Jamaica; Japan; Kenya; Kiribati; Korea, Republic of; Liberia; Madagascar; Malaysia; Maldives; Marshall Islands; Martinique; Mauritania; Mauritius; Mayotte; Mexico; Micronesia, Federated States of ; Montserrat; Mozambique; Myanmar; Nauru; New Caledonia; New Zealand; Nicaragua; Nigeria; Norfolk Island; Northern Mariana Islands; Oman; Palau; Panama; Papua New Guinea; Peru; Philippines; Pitcairn; Puerto Rico; Réunion; Saint Barthélemy; Saint Helena, Ascension and Tristan da Cunha; Saint Kitts and Nevis; Saint Lucia; Saint Martin (French part); Saint Vincent and the Grenadines; Samoa; Sao Tomé and Principe; Senegal; Seychelles; Sint Maarten (Dutch part); Solomon Islands; Somalia; South Africa; Sri Lanka; Suriname; Taiwan, Province of China; Tanzania, United Republic of; Thailand; Tokelau; Tonga; Trinidad and Tobago; Turks and Caicos Islands; Tuvalu; United States; United States Minor Outlying Islands; Vanuatu; Venezuela, Bolivarian Republic of; Viet Nam; Virgin Islands, British; Virgin Islands, U.S.; Yemen
Bahrain; Belgium; Cape Verde; Christmas Island; Côte d'Ivoire; Denmark; Eritrea; France; Germany; Ghana; Hong Kong; Iceland; Israel; Italy; Malawi; Norway; Portugal; Saudi Arabia; Sierra Leone; Spain; Sudan; Swaziland; Sweden; Togo; Tunisia; United Arab Emirates; United Kingdom; Zimbabwe
Present - origin uncertain:
Angola; Bangladesh; Benin; Cambodia; Congo; Congo, The Democratic Republic of the; Gabon; Gambia; Guinea; Guinea-Bissau; Iraq; Kuwait; Namibia; Niue; Pakistan; Timor-Leste; Wallis and Futuna
Additional data:
Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:195000000
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):50
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The global population is estimated to number c.21,000,000-22,000,000 individuals (Wetlands International 2006), while the population in Japan has been estimated at < c.100,000 breeding pairs and < c.1,000 individuals on migration (Brazil 2009).

Trend Justification:  The overall population trend is uncertain, as some populations are decreasing, while others are increasing or have unknown trends (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 species is dispersive and migratory (Higgins and Davies 1996). At most colonies adults leave for the open sea after breeding (del Hoyo et al. 1996) and become strongly pelagic (Higgins and Davies 1996) for 2-3 months before returning to the breeding grounds (del Hoyo et al. 1996). On returning to the breeding colonies they continue to forage pelagically by day and settle on land at night for a further 2-3 months before beginning to breed (del Hoyo et al. 1996). The timing of breeding varies throughout the species's range, with nesting occurring all year round at some colony sites but seasonally at others (del Hoyo et al. 1996). The species nests in very large colonies (del Hoyo et al. 1996) and remains gregarious throughout the year (congregating in small to large flocks to feed at sea) although it may be observed singly (Higgins and Davies 1996). Habitat Breeding It breeds on flat, open, sparsely or heavily vegetated, oceanic or barrier islands of sand, coral or rock in productive tropical and subtropical offshore waters rich in plankton, fish and squid (del Hoyo et al. 1996). It is absent from cold current areas and generally avoids islands with terrestrial predators (del Hoyo et al. 1996). Non-breeding Outside of the breeding season the species is highly pelagic but generally avoids cold current areas (del Hoyo et al. 1996). Diet Its diet consists predominantly of fish up to 18 cm long (usually 6-8 cm) and squid, but it also occasionally takes crustaceans, insects and offal (del Hoyo et al. 1996). The species is reliant upon prey driven to the surface by predatory fish (e.g. tuna, Scombidae), especially when breeding (Higgins and Davies 1996). Breeding site The nest is a slight depression (del Hoyo et al. 1996) or scrape on the ground (Higgins and Davies 1996). It shows a preference for nesting on flat, bare sand, coral grit or shell (Higgins and Davies 1996, del Hoyo et al. 1996) amongst low vegetation (Higgins and Davies 1996, del Hoyo et al. 1996) on beaches above the high-water mark (Higgins and Davies 1996) or on coral islands, atolls and sandbanks (Higgins and Davies 1996). Less often it may nest on rock stacks or other offshore islets, and on ledges or terraces of cliffs (although it avoids sheer cliff-faces) (Higgins and Davies 1996). It nests in dense colonies within which neighbouring nests may be placed c.50 cm apart (del Hoyo et al. 1996). Higher nesting densities occur in areas where bare ground predominates but which are vegetated with plants greater than or equal to 15 cm tall (Feare et al. 1997). Management information The mortality of the species was significantly reduced on Isla Isabel (a densely forested tropical island off the Pacific coast of Mexico) by the eradication of introduced domestic cats Felis catus using a combination of poisoning, trapping and hunting with firearms (Rodriguez et al. 2006). The nesting density and therefore the number of breeding pairs was increased in colonies on Bird Island by clearing areas of dense native or introduced vegetation and burning existing colony areas annually to prevent the growth of woody plants (Feare et al. 1997).
Systems:Terrestrial; Marine
Continuing decline in area, extent and/or quality of habitat:Unknown
Generation Length (years):10.9
Movement patterns:Full Migrant
Congregatory:Congregatory (and dispersive)

Threats [top]

Major Threat(s): Some colonies (e.g. on Ascension Island) (del Hoyo et al. 1996) are threatened by predation from introduced rats and domestic cats Felis catus (Rodriguez et al. 2006), and the species has been displaced from nesting colonies on Bird Island by invasive ants Anoplolepis longipes (Feare 1999). Persistent large scale egg-collecting in some areas has encouraged the species to move to suboptimal nesting sites, resulting in higher mortality and reduced reproductive success (van Halewyn and Norton 1984). It may also be threatened by climatic change, as variations in sea-surface temperature have been shown to negatively influence the species's foraging success at breeding colonies (hence lowering reproductive success) (Erwin and Congdon 2007). The species is vulnerable to oil pollution from oil spills and tankers transporting fuel (del Hoyo et al. 1996) and is threatened by reductions in the global populations of tuna (a result of over-fishing) due to it's dependence on tuna to force prey to the surface (Reichel 1991). Utilisation The eggs of this species are harvested in many areas (e.g. Caribbean) (van Halewyn and Norton 1984, del Hoyo et al. 1996).

Amended [top]

Amended reason: Map revised. Edited origin of occurrence for Togo. Added a Contributor.

Citation: BirdLife International. 2017. Onychoprion fuscatus (amended version of 2016 assessment). The IUCN Red List of Threatened Species 2017: e.T22694740A110635097. . Downloaded on 16 August 2018.
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