760 A PRACTICAL HANDBOOK OF BRITISH BIRDS. 



Fourth winter and summer. — As adult but probably backward 

 birds are as described under third winter but rather less brownish 

 and with white tails, while most are indistinguishable from adults 

 except for black streaks on primary-coverts. 



Measurements and structure. — $ wing 410-435 mm. (juv. 397- 

 425), tail 148-165, tarsus 62-71, bill from feathers 50-56 (juv. 46-51) 

 (12 measured). ? wing 385-405 (juv. 370-390), bill 45-51 (juv. 41- 

 47). Primaries : 1st narrow, pointed and about two-thirds primary- 

 coverts, 2nd longest, 3rd 3-10 mm shorter but sometimes as long, 

 4th 15-30 shorter, 5th 40-55 shorter. Rest of structure as Herring- 

 Gull but tarsus and toes slightly more slender. 



Soft parts. — Bill as described under Herring-Gull ; legs and 

 feet (ad.) bright yellow, (juv. and 1st winter and summer) pale 

 brownish-flesh, (2nd winter to 3rd winter) pale creamy-flesh with 

 yellowish varying, (3rd summer) pale cream to yellow ; iris as in 

 Herring-Gull ; orbital ring vermilion. 



Characters and allied forms. — For differences of L. f. fuscus 

 see under that form. L. f. taimyrensis (N. Russia, Siberia) is like 

 L. f. affinis but larger. Slate-grey mantle and wings and yellow 

 legs distinguish adult, for distinctions of juvenile see description, 

 in other stages mantle and wings always darker than in Herring- 

 Gull. 



Field -characters. — Adult resembles Greater Black-backed Gull 

 but is much smaller, has yellow feet, and upper-parts are slate-grey 

 rather than black, although in L. f. fuscus the tint is as deep as in 

 the larger bird. Juvenile like that of Herring-Gull but slightly 

 darker. In their slow progress to maturity the two species become 

 easier to discriminate with each successive moult. Seen inland 

 oftener than Herring-Gull especially at migration times. A wailing 

 " kee-yah " and other cries akin to those of Herring-Gull, but 

 usual alarm note at nesting-place is a guttural " ug, ug, ug." 



Breeding-habits. — Nests usually in colonies, often on moors and 

 flows at some distance inland, but also on grassy cliffs and flat- 

 topped islands. Nest. — Composed of any material at hand, heather, 

 grass, seaweed, etc. Eggs. — Usually 3, but sometimes 2 only, while 

 4 have been recorded. Ground-colour varies from pale greenish- 

 blue to dark umber-brown, usually spotted and blotched with 

 blackish-brown, occasionally very sparsely marked. Average of 

 100 eggs, 67.95x47.26. Max. : 77.1x49 and 72.5x52.1. Min. : 

 58.6x45 and 61.3x43 mm. Breeding -season. — From early May 

 onward to June. Incubation. — Probably by both sexes, but con- 

 firmation desirable. Period said to be 21 days (Paynter), but 

 estimate appears low. Single brooded. 



Food. — Almost omnivorous : seen to kill Puffin (probably also 

 Manx Shearwater), young Lapwing, etc., and devours carcases o 

 dead mammals and birds ; destructive to eggs of other specie 

 (Cormorant, Eider, Mallard, Grouse, Terns, and smaller birds) 



