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.

Family/Sub-family Laridae

Species name author Pallas, 1764

Taxonomic source(s) AERC TAC (2003), AOU checklist (1998 + supplements), Christidis and Boles (1994), Christidis and Boles (2008), Cramp and Simmons (1977-1994), Dowsett and Forbes-Watson (1993), Sibley and Monroe (1990, 1993), Turbott (1990)

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

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.

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

190,000 - 410,000

unset

11,800,000 km²

No

Range & 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 Hawaii¹.

Important Bird Areas Click here to view map showing IBAs where species is recorded and triggers any of the IBA criteria.

Ecology: Behaviour The Little Tern is a strongly migratory¹ 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 July² in solitary pairs³ or small monospecific groups¹ usually of 1-15 pairs^1,4 (rarely over 40 pairs)¹ occasionally amidst colonies of other terns³. Breeding may be timed to coincide with peak fish abundance¹⁵. Northern breeders depart the breeding grounds from late-July onwards^1,2, travelling first to moulting sites where they form large roosts before continuing southwards⁹. The species is gregarious throughout the year⁴ and usually feeds singly, in small groups or larger scattered flocks⁴ and congregating in many thousands on passage in small wetlands where fish fry are abundant¹. Habitat Breeding The species breeds on barren or sparsely vegetated beaches, islands and spits of sand, shingle¹, shell fragments, pebbles³, rocks or coral fragments¹ on seashores³ or in estuaries, saltmarshes, saltpans, offshore coral reefs¹, rivers, lakes^1,3 and reservoirs⁶. It may also nest on dry mudflats in grassy areas^1,6 but shows a preference for islets surrounded by saline or fresh water where small fish can be caught without the need for extensive foraging flights⁴. Non-breeding Outside of the breeding season the species frequents tidal creeks, coastal lagoons and saltpans and may foraging at sea¹ up to 15 km offshore⁵. 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 molluscs¹. In Scotland, Little Terns feed mainly on small fish and invertebrates, including herring, sandeel, and shrimps (Crangon vulgaris)¹⁷. 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 areas¹⁶. 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 sprat¹⁸. Breeding site The nest is a bare scrape² positioned on the ground in less than 15 % vegetation cover¹ on beaches of sand, pebbles, shingle, shell fragments, coral fragments or rock^1,3 above the high tide-line and often only a few metres away from shallow clear water⁴. Alternatively in more marshy habitats (e.g. coastal saltmarshes) the species may build a nest of shells or vegetation¹. The species nests in small loose colonies, with neighbouring nests usually placed more than 2 m apart¹. Foraging range In Spain, 95% of foraging terns were observed less than 4 km away from the nearest colony¹⁹. 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 km¹⁵, whereas failed birds ranged widely, travelling up to 27 km in a single foraging bout¹⁵. In Portugal, ranges were found to be significantly greater during incubation (April-May) than during chick rearing (June-July)²⁰. Little Terns prefer channels and lagoons for foraging, rather than deeper marine habitats^19,20. They also prefer areas with abundant resources, entrance channels and main lagoon channels with strong currents, and areas with alternative feeding resources nearby²⁰. Areas subjected to strong human pressure²⁰ and salt marshes¹⁹ are avoided. The species tends to forage preferentially at low tide²⁰.

Threats The species is threatened by habitat destruction⁷ such as the development and industrial reclamation of coastal breeding habitats^{1, 7} (e.g. for the development of new harbour facilities)⁷. It is also highly vulnerable to human disturbance (including birdwatchers) at coastal and inland nesting sites which can lead to nest failures^{1, 7}. Pesticide pollution (e.g. organochlorine pollutants, mercury and DDT)^{7, 10, 12} and artificially induced water-level fluctuations in saltmarshes⁷ may also pose a threat to the species's reproductive success^{7, 10, 12}. The species also suffers from local egg collecting⁷ and is susceptible to avian influenza so may be threatened by future outbreaks of the virus⁸.

Conservation measures 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^2,11. 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 season¹¹. 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)¹³. 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 sites¹⁴. 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 species¹⁴.

References 1. del Hoyo et al. (1996). 2. Richards (1990). 3. Flint et al. (1984). 4. Snow and Perrins (1998). 5. Urban et al. (1986). 6. de Silva (1991). 7. Barcena et al. (1984). 8. Melville and Shortridge (2006). 9. Tavecchia et al. (2006). 10. Choi et al. (2001). 11. Medeiros et al. (2007). 12. Thyen et al. (2000). 13. Burgess and Hirons (1992). 14. Fasola and Canova (1996). 15. Perrow et al (2006). 16. Catry et al (2006). 17. BirdLife International (2000). 18. Taylor and Roe (2004). 19. Bertolero et al (2005). 20. Paiva et al (2007).

Further web sources of information

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

Text account compilers Stuart Butchart (BirdLife International), Rob Calvert (BirdLife International), Jonathan Ekstrom (BirdLife International), Jess Hatchett (BirdLife International), Lucy Malpas (BirdLife International)

IUCN Red List evaluators Jeremy Bird (BirdLife International), Stuart Butchart (BirdLife International)

Recommended citation BirdLife International (2010) Species factsheet: Sterna albifrons. Downloaded from http://www.birdlife.org on 30/7/2010

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.

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