THE BLACK TERN. 689 



Terns by deeply incised webs and from other Chlidonias in 

 summer by blackish chin and slate-grey lesser wing-coverts, 

 and in juvenile and winter by brown patches on sides of 

 breast. 



Field -characters. — Adult in breeding plumage unlike any other 

 British Tern except the rarer C. leucopterus, which has white carpus 

 and tail. Immature Black and White-winged Black Terns probably 

 indistinguishable in the field, but differ from other Terns in having 

 only slightly forked tail. Bulk of food taken in air, or picked deftly 

 from surface of water during flight. Seldom splashes into water, 

 and rarely if ever submerges as other Terns do. Migrants passing 

 through Britain usually silent ; a note occasionally heard is a 

 reiterated " tcherk," and cry at breeding places is a shrill " crick, 

 crick." 



Breeding-habits. — Nests in colonies in marshes, lagoons, etc., 

 generally in shallow water. Nest. — Floating heap of water -weeds, 

 reeds, etc., more neatly lined than that of Whiskered Tern and with 

 finer materials. Eggs. — Usually 3, but sometimes 2 only, ground- 

 colour ochreous or brownish to greenish, heavily blotched with 

 blackish-brown, often in zone round large end, and ashy shellmarks. 

 Average of 100 eggs, 34.8x25.1. Max. : 40.2x25 and 35x27.4. 

 Min. : 30.5x24.5 and 32.4x23.5 mm. Breeding -season. — From 

 about mid May in Spain and a week or so later in Central Europe, 

 onward. Incubation. — Shared by sexes, but chiefly by female 

 (Naumann). Period 14-16 days. Single brooded. 



Food. — Mainly insects and their larvae : coleoptera (waterbeetles, 

 Poecilus, Aphodius, Amara, Donacia, Anisoplia), orthoptera (Acheta, 

 Gomphocerus), diptera (larvae of Tipulidce, Helophila, etc.), hymenop- 

 tera (Formica rufa, F. fusca, etc.), odonata (Agrion, Libellula), 

 phryganeidae (Limnophilus) , and Notonecta. Naumann also includes 

 small fish, tadpoles, and small frogs. 



Distribution. — England and Wales. — Passage-migrant, mid-April 

 to 2nd week June and mid- July to end Sept. (occasionally later). 

 Chiefly south, and east England up to Yorks., where annual but 

 rarer, as it is inland, including midlands. More irregular west coast 

 and Wales. North of Yorks. and Lanes., rare. Often in flocks. 

 Formerly bred various parts, last definite records Solway, 1855, Nor- 

 folk, 1858. Scotland.— Occasional Tweed and Forth, rare vagrant 

 elsewhere, recorded O. Hebrides (May, 1913), Orkneys (Oct., 1913 ; 

 June, 1918). Ireland. — Rare vagrant to all Provinces. Has occurred 

 July, Aug., Sept., Nov., and Dec. 



Distribution. — A broad.— Breeds in Europe south of about 60° 

 north lat., south to south Spain, Mallorca, Rumania, and Bulgaria. 

 North Asia east to about 85° long., south to Caspian Sea. Winters 

 in Africa south to Loango in west and Tanganyika Territory in east. 

 Once Faeroes. Replaced in N. America (in summer) and in S. 

 America (in winter) by C. n. surinamensis . 



VOL. II. 2 Y 



