sabine's gull. 723 



primary-coverts, 2nd longest, 3rd equal or 2-7 mm. shorter, 4th 

 15-25 shorter, 5th 32-45 shorter ; outer web of 2nd narrow. Outer 

 secondaries shorter than 11th primary, tips fairly square, tips of 

 rest sloped off on outer webs, innermost about as long as 7th 

 primary, tips sharply rounded. Tail forked, 12 feathers, tips 

 somewhat rounded. About one-third of tibia bare, tarsus slender, 

 toes rather short, hind one minute and elevated, three front ones 

 connected by slightly concave webs, claws short and somewhat 

 dilated. Bill compressed, upper mandible straight for two-thirds 

 then curving to tip, gonys sharply sloped up, angle not very 

 prominent. 



Soft parts. — Bill (ad.) black, tip yellow, (juv. dusky) ; legs and 

 feet dusky-grey ; iris dark brown ; orbital ring and inside mouth 

 vermilion. 



Characters. — No subspecies. Forked tail distinguishes it from 

 other British gulls, bill and white-tipped black primaries from any 

 British Terns. 



Field -characters. — Quite a small bird, not much larger than 

 Common and Arctic Terns, and rivalling them in lightness and 

 activity on the wing. In breeding plumage black head and black 

 edge to fore-wing are very conspicuous in flight and in combination 

 with small size and white forked tail render it unmistakable. Has 

 a harsh angry chattering note quite unlike that of any Tern. When 

 at rest wings appear to be barred with black near tips. (F. C.R.J.) 



Breeding-habits. — Haunts islets in swampy tundra or off coast, 

 often in close proximity to ice and in company with Arctic Tern. 

 Nest. — Slight, composed of stalks and bits of vegetable matter 

 arranged in a scrape in marshy ground. Eggs. — Normally 3, some- 

 times 2 only. Brownish or greenish-olive in ground-colour, rather 

 sparingly spotted and blotched olive-brown. Average of 50 eggs, 

 44.43x32.24. Max.: 49.2x33 and 43.2x33.9. Min. : 41.0X 

 31.5 and 43.6x29.8 mm. Breeding -season. — In Alaska from end 

 May and first week June, but in high latitudes of Old World (Spits- 

 bergen, etc.) about July 7. Incubation. — Apparently by both 

 sexes. Period unknown. Probably single brooded ; undoubtedly 

 so in high north. 



Food. — Insects and their larvae, chiefly diptera ; also mollusca 

 (Mytilus), small Crustacea, annelida and, according to Bent, small 



fishes. 



Distribution. — British Isles. — Scarce autumn and winter-visitor, 

 rarely in spring and summer. Most frequent Yorks. and Norfolk,, 

 many recorded at intervals elsewhere, even in inland counties, but. 

 rarer Scotland (unrecorded O. Hebrides) and only twelve Ireland 

 (Dublin Bay seven, Belfast Lough three, Donegal Bay one, Lough. 

 Derg one). Adults very rare. 



Distribution. — Abroad. — Breeds on coasts of Siberia : Anadyr, 

 delta of Lena, Taimyr Peninsula, on Spitsbergen, and on coast of 



