Species

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). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable 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.

Taxonomic source(s)
AERC TAC. 2003. AERC TAC Checklist of bird taxa occurring in Western Palearctic region, 15th Draft. Available at: http://www.aerc.eu/DOCS/Bird_taxa_of _the_WP15.xls.
AOU. 1998. Check-list of North American birds. American Ornithologists' Union, Washington, D.C.
Christidis, L.; Boles, W. E. 1994. The taxonomy and species of birds of Australia and its territories. Royal Australasian Ornithologists' Union, Melbourne.
Christidis, L.; Boles, W. E. 2008. Systematics and taxonomy of Australian birds. CSIRO Publishing, Collingwood, Australia.
Cramp, S.; Perrins, C. M. 1977-1994. Handbook of the birds of Europe, the Middle East and Africa. The birds of the western Palearctic. Oxford University Press, Oxford.
Dowsett, R. J.; Forbes-Watson, A. D. 1993. Checklist of birds of the Afrotropical and Malagasy regions. Tauraco Press, Li
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.
Turbott, E. G. 1990. Checklist of the birds of New Zealand. Ornithological Society of New Zealand, Wellington.

Taxonomic note
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.

Synonym(s)
Sternula albifrons AOU checklist (1998 + supplements), Sternula albifrons Christidis and Boles (2008), Sternula albifrons , Sternula albifrons albifrons Christidis and Boles (2008)

Distribution and population
Breeding populations of the Little Tern can be found through much of Europe, scattering along the coast and inland in parts of Africa, in much of western, central and the extreme east and south of Asia, and in northern parts of Australasia. Migratory individuals expand the range to include most of the coast of Africa, the Arabian Peninsula, the western coast of India and most of the waters of south-east Asia and Australasia, including New Zealand. One seasonally breeding colony is also present on Hawaii (del Hoyo et al. 1996).

Population justification
The global population is estimated to number c.190,000-410,000 individuals (Wetlands International 2006), while national population estimates include: c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in China; c.100-10,000 breeding pairs, c.50-1,000 individuals on migration and c.50-1,000 wintering individuals in Taiwan; c.100-10,000 breeding pairs and c.50-1,000 individuals on migration in Korea 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 decreasing, although some populations have unknown trends (Wetlands International 2006).

Ecology
Behaviour The Little Tern is a strongly migratory (del Hoyo et al. 1996) coastal seabird which usually fishes in very shallow water only a few centimetres deep, often over the advancing tideline or in brackish lagoons and saltmarsh creeks. It has the most inshore distribution of all terns. It breeds between May and July (Richards 1990) in solitary pairs (Flint et al. 1984) or small monospecific groups (del Hoyo et al. 1996) usually of 1-15 pairs (del Hoyo et al. 1996, Snow and Perrins 1998) (rarely over 40 pairs) (del Hoyo et al. 1996) occasionally amidst colonies of other terns (Flint et al. 1984). Breeding may be timed to coincide with peak fish abundance (Perrow et al 2006). Northern breeders depart the breeding grounds from late-July onwards (Richards 1990, del Hoyo et al. 1996), travelling first to moulting sites where they form large roosts before continuing southwards (Tavecchia et al. 2006). The species is gregarious throughout the year (Snow and Perrins 1998) and usually feeds singly, in small groups or larger scattered flocks (Snow and Perrins 1998) and congregating in many thousands on passage in small wetlands where fish fry are abundant (del Hoyo et al. 1996). Habitat Breeding The species breeds on barren or sparsely vegetated beaches, islands and spits of sand, shingle (del Hoyo et al. 1996), shell fragments, pebbles (Flint et al. 1984), rocks or coral fragments (del Hoyo et al. 1996) on seashores (Flint et al. 1984) or in estuaries, saltmarshes, saltpans, offshore coral reefs (del Hoyo et al. 1996), rivers, lakes (Flint et al. 1984, del Hoyo et al. 1996) and reservoirs (de Silva 1991). It may also nest on dry mudflats in grassy areas (de Silva 1991, del Hoyo et al. 1996) but shows a preference for islets surrounded by saline or fresh water where small fish can be caught without the need for extensive foraging flights (Snow and Perrins 1998). Non-breeding Outside of the breeding season the species frequents tidal creeks, coastal lagoons and saltpans and may foraging at sea (del Hoyo et al. 1996) up to 15 km offshore (Urban et al. 1986). Diet Its diet consists predominantly of small fish (e.g. Ammodytes spp., roach Rutilus rutilus, rudd Scardinius erythrophthalmus, carp Cyprinus carpio and perch Perca fluviatilis) and crustaceans 3-6 cm long as well as insects, annelid worms and molluscs (del Hoyo et al. 1996). In Scotland, Little Terns feed mainly on small fish and invertebrates, including herring, sandeel, and shrimps (Crangon vulgaris) (BirdLife International 2000). In Portugal, birds were found to feed mainly on sand-smelts (Atherina spp.) and gobies (Pomatoschistus spp.), which were the most abundant fish species in the study areas (Catry et al 2006). On Rigby Island, Australia, chicks were fed entirely on juvenile fish of the families Clupeidae, Engraulidae, Pomatomidae and Carangidae, including pilchard, southern anchovy and blue sprat (Taylor and Roe 2004). Breeding site The nest is a bare scrape (Richards 1990) positioned on the ground in less than 15 % vegetation cover (del Hoyo et al. 1996) on beaches of sand, pebbles, shingle, shell fragments, coral fragments or rock (Flint et al. 1984, del Hoyo et al. 1996) above the high tide-line and often only a few metres away from shallow clear water (Snow and Perrins 1998). Alternatively in more marshy habitats (e.g. coastal saltmarshes) the species may build a nest of shells or vegetation (del Hoyo et al. 1996). The species nests in small loose colonies, with neighbouring nests usually placed more than 2 m apart (del Hoyo et al. 1996). Foraging range In Spain, 95% of foraging terns were observed less than 4 km away from the nearest colony (Bertolero et al 2005). However, the foraging range of individuals varies according to whether they are currently breeding. In Norfolk, UK, birds with an active nest occupied a range of <6.3 km² with a range span of up to 4.6 km (Perrow et al 2006), whereas failed birds ranged widely, travelling up to 27 km in a single foraging bout (Perrow et al 2006). In Portugal, ranges were found to be significantly greater during incubation (April-May) than during chick rearing (June-July) (Paiva et al 2007). Little Terns prefer channels and lagoons for foraging, rather than deeper marine habitats (Bertolero et al 2005, Paiva et al 2007). They also prefer areas with abundant resources, entrance channels and main lagoon channels with strong currents, and areas with alternative feeding resources nearby (Paiva et al 2007). Areas subjected to strong human pressure (Paiva et al 2007) and salt marshes (Bertolero et al 2005) are avoided. The species tends to forage preferentially at low tide (Paiva et al 2007).

Threats
The species is threatened by habitat destruction (Barcena et al. 1984) such as the development and industrial reclamation of coastal breeding habitats (Barcena et al. 1984, del Hoyo et al. 1996) (e.g. for the development of new harbour facilities) (Barcena et al. 1984). It is also highly vulnerable to human disturbance (including birdwatchers) at coastal and inland nesting sites which can lead to nest failures (Barcena et al. 1984, del Hoyo et al. 1996). Pesticide pollution (e.g. organochlorine pollutants, mercury and DDT) (Barcena et al. 1984, Thyen et al. 2000, Choi et al. 2001) and artificially induced water-level fluctuations in saltmarshes (Barcena et al. 1984) may also pose a threat to the species's reproductive success (Barcena et al. 1984, Thyen et al. 2000, Choi et al. 2001). The species also suffers from local egg collecting (Barcena et al. 1984) and is susceptible to avian influenza so may be threatened by future outbreaks of the virus (Melville and Shortridge 2006).

Conservation actions underway
Protective measures such as fencing-off sensitive nesting areas, erecting warning signs and wardening are effective measures of increasing the breeding success of this species on sandy beaches (Richards 1990, Medeiros et al. 2007). There is also evidence that earlier breeders benefit more (i.e. have higher reproductive success) from protective measures, suggesting that conservation efforts can be maximised if concentrated earlier in the season (Medeiros et al. 2007). Breeding pairs are also 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). A conservation scheme for the protection of gull and tern breeding colonies in coastal lagoons and deltas (e.g. Po Delta, Italy) involves protection from human disturbance, prevention of erosion of islet complexes, habitat maintenance and the creation of new islets for nest sites (Fasola and Canova 1996). The scheme particularly specifies that small bare islets of 0.1-0.8 ha with very reduced vegetation cover (less than 30 %) and sward heights less than 20 cm should be maintained or created as additional nesting sites for this species (Fasola and Canova 1996).

References
Flint, V. E.; Boehme, R. L.; Kostin, Y. V.; Kuznetsov, A. A. 1984. A field guide to birds of the USSR. Princeton University Press, Princeton, New Jersey.

Urban, E. K.; Fry, C. H.; Keith, S. 1986. The birds of Africa vol. II. Academic Press, London.

Richards, A. 1990. Seabirds of the northern hemisphere. Dragon's World Ltd, Limpsfield, U.K.

Fasola, M.; Canova, L. 1996. Conservation of gull and tern colony sites in north-eastern Italy, an internationally important bird area. Colonial Waterbirds 19: 59-67.

del Hoyo, J.; Elliott, A.; Sargatal, J. 1996. Handbook of the Birds of the World, vol. 3: Hoatzin to Auks. Lynx Edicions, Barcelona, Spain.

Snow, D. W.; Perrins, C. M. 1998. The Birds of the Western Palearctic vol. 1: Non-Passerines. Oxford University Press, Oxford.

BirdLife International. 2000. The Development of Boundary Selection Criteria for the Extension of Breeding Seabird Special Protection Areas into the Marine Environment. OSPAR Convention for the Protection of the Marine Environment of the North-East Atlantic. Vlissingen (Flushing).

Barcena, F.; Teixeira, A. M., Bermejo, A. 1984. Breeding seabird populations in the Atlantic sector of the Iberian Peninsula. In: Croxall, J. P.; Evans, P. G. H., Schreiber, R. W. (ed.), Status and Conservation of the World's Seabirds, pp. 335-345. International Council for Bird Preservation.

Melville, D. S.; Shortridge, K. F. 2006. Migratory waterbirds and avian influenza in the East Asian-Australasian Flyway with particular reference to the 2003-2004 H5N1 outbreak. In: Boere, G.; Galbraith, C., Stroud, D. (ed.), Waterbirds around the world, pp. 432-438. The Stationary Office, Edinburgh, UK.

Tavecchia, G.; Baccetti, N.; Serra, L. 2006. Modelling survival and movement probability of Little Tern Sterna albifrons at a post-breeding moulting site: the effect of the colony of origin. In: Boere, G.; Galbraith, C., Stroud, D. (ed.), Waterbirds around the world, pp. 560-561. The Stationary Office, Edinburgh, UK.

Burgess, N. D.; Hirons, J. M. 1992. Creation and management of articficial nesting sites for wetland birds. Journal of Environmental Management 34(4): 285-295.

Choi, J. W.; Matsuda, M.; Kawano, M.; Min, B. Y.; Wakimoto, T. 2001. Accumulation Profiles of Persistent Organochlorines in Waterbirds from an Estuary in Korea. Archives of Environmental Contamination and Toxicology 41: 353-363.

de Silva, R. I. 1991. Status and conservation of the breeding seabirds of Sri Lanka. In: Croxall. J. P. (ed.), Seabird Status and Conservation: A Supplement, pp. 205-211. International Council for Bird Preservation, Cambridge, UK.

Medeiros, R.; Ramos, J. A.; Paiva, V. H.; Almeida, A.; Pedro, P.; Antunes, S. 2007. Signage reduces the impact of human disturbance on little tern nesting success in Portugal. Biological Conservation 135: 99-106.

Thyen, S.; Becker, P. H.; Behmann, H. 2000. Organochlorine and mercury contamination of little terns (Sterna albifrons) breeding at the western Baltic Sea, 1978-96. Environmental Pollution 108: 225-238.

Catry, T., Ramos, J.A., Martins, J., Peste, F., Trigo, S., Paiva, V.H., Almeida, A., Luis, A., Palma, J. and Andrade, P.J. 2006. Intercolony and annual differences in the diet and feeding ecology of little tern adults and chicks in Portugal. Condor 108(2): 366-376.

Perrow, M. R., Skeate, E. R., Lines, P., Brown, D., Tomlinson, M. L. 2006. Radio telemetry as a tool for impact assessment of wind farms: the case of Little Terns Sterna albifrons at Scroby Sands, Norfolk, UK.

Taylor IR; Roe EL. 2004. Feeding ecology of little terns Sterna albifrons sinensis in south-eastern Australia and the effects of pilchard mass mortality on breeding success and population size . Marine and Freshwater Research 55(8): 799-808.

Further web sources of information
Detailed species account from Birds in Europe: population estimates, trends and conservation status (BirdLife International 2004)

View photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Butchart, S., Calvert, R., Ekstrom, J., Hatchett, J., Malpas, L.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2013) Species factsheet: Sterna albifrons. Downloaded from http://www.birdlife.org on 23/05/2013. Recommended citation for factsheets for more than one species: BirdLife International (2013) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/05/2013.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

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Additional resources for this species

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