Black-bellied Tern Sterna acuticauda Scientific name definitions

32–35 cm. Typical tern from above, with black cap and grey back and wings, latter long and pointed; throat white, breast pale grey shading into deep black and brownish-black belly and undertail-coverts; dark underparts contrast with white underwing, latter with darker band across secondaries; bill yellow-orange; legs reddish orange. Non-breeding adult has white forecrown streaked black, black band behind eye, whitish underparts mottled black on belly, and black tip to bill. Juvenile has red at base of mandible and blackish feet; can be confused with “portlandica” plumage of S. hirundo, but darker.

Pakistan (R Indus) and along major river systems of India E to C Bangladesh and Assam Valley. Now very rare in S China (W Yunnan), Nepal and Myanmar, and probably extinct in NW Thailand, Laos, Cambodia and S Vietnam (1 BirdLife International (2013). IUCN Red List for birds. URL: http://www.birdlife.org (download Aug 2013). Close ).

Inland lakes and rivers , preferring broad, barren, featureless flats, sand spits and sandy islands in rivers. Forages along rivers and lakes, and over paddies, ditches and village ponds. Occurs up to 700 m in Nepal.

Gives short, full, dog-like barks, e.g. “nyap” or “nyark”, which vary slightly in pitch and are only heard irregularly, but sometimes in short series at rate of 3–4 notes/second.

Feb –May. Early nests sometimes flooded. Often breeds with S. aurantia, skimmers and pratincoles, but not colonial; nests very widely spaced, often more than 1 km and essentially solitary. Shallow, unlined scrape in bare sand, sometimes near a small object; usually more than 200 m from water’s edge. Clutch three eggs, sometimes two, rarely four; incubation and fledging not studied, and reports of 15–16 days and eight weeks, respectively, certainly erroneous; adults shade eggs and chicks, and also sprinkle water from belly feathers; adults mob intruding birds and predators. Productivity: one report of 0·7 young/nest.

ENDANGERED. The total population is believed to number fewer than 10,000 individuals and is in continuing decline. Now very rare, possibly extinct, in Thailand: sightings of single individuals at Krabi and Bung Boraphet, Thailand, in April 2003 and April 2004 respectively are noteworthy (2 Jansen, J.J.F.J. (2005). Black-bellied Tern at Krabi, Thailand, in April 26626623. Dutch Birding. 27: 202–203. Close ) ; disappearing from Laos and Cambodia; no more than 25 pairs in Myanmar. Said to be common resident in Nepal, and fairly common in N & C India , but few recent sightings (3 Sykes, B.R. (2010). River terns: is the Black-bellied Tern Sterna acuticauda heading to oblivion? BirdingASIA. 13: 73. Close , 4 Aarif, K. M., S. Babu, and S. V. A. Hameed (2010). Distribution of the Black-bellied Tern Sterna acuticauda Gray in Kerala, South India. Podoces 5(1): 69–70. Close ). Very rare in Bangladesh, where an intensive and extensive search of two major rivers between Dec 2011 and Apr 2012 failed to find any (5 Chowdhury, S.U., Foysal, M., Sharpe, J. and Shahadat, O. (2014). A survey for Black-bellied Tern Sterna acuticauda and other riverine birds on the Jamuna and Padma rivers in Bangladesh. Forktail. 30: 84–89. Close ), but the species was discovered breeding again in May 2016, the first record since 2000 (6 Kabir, M.T., Chowdhury, S.U., Tareq, O., Alam, A.B.M.S., Ahmed, S., Shahadat, O. and Foysal, M. (2016). New breeding records of riverine birds in Bangladesh. BirdingASIA. 26: 39–42. Close ). Destruction of breeding habitats is a major threat; eggs widely collected for food; and nests subject to flooding. Wide nest dispersion presumably an adaptation to heavy pressure from terrestrial predators, including man.