[order] Charadriiformes | [family] Sternidae | [latin] Gelochelidon nilotica | [UK] Gull-Billed Tern | [FR] Sterne hansel | [DE] Lachseeschwalbe | [ES] Gaviotín de Pico Negro | [IT] Sterna zampenere | [NL] Lachstern

Lachstern determination

copyright: J. del Hoyo

Unique heavy-billed, long-legged tern whit slightly formed tail, broad wings and very pale body. 35-40 cm, 130-300 g, wingspan 85-100 cm. All black bill has sharp gonydeal angle, but no terminal hook, resembling that of small gull. Eye dark brown, crown and nape black, upperparts including rump pale grey, primaries slightly darker but wingtips whitish to pale grey. Tail and underparts white. Races differ mainly in size, especially of bill and also in color tone of upperparts. macrotarsa is largest race, especially in bill and feet.

Breeds on barrier beaches and dunes, salt marshes, and rivers and freshwater lagoons. Far more along coastal plains then in continental interiors, but also breeds on hypersaline lakes. Often feeds in large numbers on emerging insects over lakes, fields and grassland and even over semi desert. Winters on estuaries, lakes and salt-pans.

Sterna nilotica is a patchily distributed breeder in southern and eastern Europe, which accounts for less than a quarter of its global breeding range. Its European breeding population is relatively small (<22,000 pairs), and declined substantially between 1970- 1990. Although the species was broadly stable in south-west Europe and Russia during 1990-2000, it declined in south-eastern Europe, and continued to decline overall at a rate that—on top of earlier declines—probably equates to a large decline (>30%) over three generations. Consequently, it is provisionally evaluated as Vulnerable.
This tern has a nearly world-wide but extremely fragmented distribution. In Europe it is breeding mainly in the Mediterranean and Black Sea regions, but a small population survives in northern Germany and Denmark. These European populations are wintering in sub-Saharan Africa. The total population of the European Union is definitely declining since the 1970's, and currently estimated at 2700 breeding pairs

More insectivorous than most other terns, prey including mainly grasshoppers, dragonflies, moths and grubs, also takes spiders, earthworms small reptiles and frogs, small fish and aquatic invertebrates. Flies slowly and then darts swiftly down to seize prey item from surface of ground, water or vegetation. Occasionally pirates food from other terns.

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 79,000-310,000 individuals (Wetlands International 2002). 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. [conservation status from birdlife.org]

Breeds May-June in North America and Europe, April-May in India and October-December in Australia. Loosely to densely colonial. Nests are built on barren beaches, on sand, shell bars, dry mud, dykes, sea wrack, floating vegetation and nesting on roofs. 2-3 eggs are laid incubated for 23 days. Chicks are white, usually unspotted. Parents attend young for 3 months. Returns to colony at 4 years old, but first breeding at 5 years.

Migratory. Wintering range of north and west European and probably Tunisian birds extends from Mauritania east to Nigeria and Chad. Populations from Balkan peninsula and Ukraine probably winter from Sudan south to Botswana. Migrants probably regularly cross Sahara, at least on spring passage, though many western migrants reach West African winter quarters via Atlantic coast. Southward movement from north of range (Denmark) begins July, with return in late April.