714 A PRACTICAL HANDBOOK OF BRITISH BIRDS. 



tip very occasionally blackish, (juv. and 1st summer) black, base of 

 lower mandible usually dull crimson ; legs and feet (ad. winter) 

 blackish, (ad. summer) coral-red, (juv.) reddish -orange, (1st summer) 

 very dark crimson, blackish in front of tarsus ; iris dark brown. 



Characters. — No subspecies. Birds from Antarctic, described as 

 distinct (antistropha), do not appear to differ from northern 

 examples. Distinguished from Common and Roseate Terns at all 

 ages by shorter tarsus and usually shorter bill, from Common by 

 usually narrower blackish line on inner web of outer primary and by 

 other differences described above, from Roseate by dark outer web 

 of outer tail-feather, longer wing, and other differences described 

 under that species. 



Field -characters. — Difficult to distinguish in the field from 

 Common (q.v.). Call-notes a sharp " tchick, tchick, tchick," and a 

 clear hawk-like whistle ; alarm-note harsh, short "kare " or "kaah." 



Breeding-habits. — Breeds generally on rocky islets in British 

 Isles but also occasionally by fresh-water lakes. Nest. — Usually 

 none, eggs laid in hollow in rock or sand. Eggs. — Normally 2 and 

 occasionally 3 or rarely 1 only. Usually more boldly marked than 

 those of Common Tern : varying from stone -colour to pale blue or 

 light to dark brown, blotched and spotted with rich dark brown 

 and ashy shellmarks, Erythristic variety also occurs in the species. 

 Average of 100 eggs, 40.7x29.5. Max. : 47x29 and 44.7x32.2. 

 Min. : 35.5x28 and 36.6x27.4 mm. Breeding -season. — Usually 

 from early June or end of May onward. Incubation. — Shared by 

 sexes. Period 20 days (Paynter). Single brooded. 



Food. — Largely small fish : including the genera Clupea, Gaster- 

 osteus, etc. Also various species of Crustacea (Gammarus, Clio, 

 Hippolyte, etc.) ; mollusca and insects (coleoptera, lepidoptera, and 

 larvse, diptera and larvse, etc.), and annelids. 



Distribution. — British Isles. — Summer -resident (end April to 4th 

 week Oct.). England and Wales. — Breeds only Fame Isles (Northum.), 

 Scilly Isles, three groups of islets off Anglesey, Walney (Lanes.), and 

 Isle of Man. Elsewhere pas sage -migrant (end April to end May and 

 early Aug. to end Oct.) and often inland. Scotland. — Breeds all 

 coasts and groups of islands, and outnumbers S. hirundo on west 

 side north of Loch Broom and in Orkneys and Shetlands, and is 

 chief breeding species O. Hebrides. Ireland. — On coasts and some 

 lakes. More numerous than 8. hirundo. 



Distribution. — Abroad. — Breeds in Iceland, Faeroes, Lapland, Fin- 

 land, Estland, coasts of North Sea south to Holland, Spitsbergen, 

 Franz Josef Land, north Russia, coasts and lower courses of rivers 

 of Siberia east to Anadyr and Commander Is. Also Greenland and 

 N. America from Alaska and British Columbia to Maine. (Breeding- 

 places near Rugen in Baltic and in Massachusetts abandoned). 

 Migrant in winter on coasts of Africa, to New Zealand, and 

 Antarctic seas ; apparently no record for south Asia. 



