THE GREAT BLACK-HEADED GULL. 743 



aries takes place Dec -April. Mantle and scapulars become more 

 slate-grey and new slate-grey feathers are scattered among old 

 worn wing-coverts and usually innermost secondaries. 



Second winter. — Head mostly white but round and behind eye 

 and back of crown streaked black-brown ; back of neck pale ash- 

 grey to whitish with varying number of dark brown or brown tipped 

 feathers ; mantle, scapulars and back slate-grey rather duller than 

 in adult and some feathers (varying in number) with dark brown 

 tips or spots ; rump, upper tail-coverts and under-parts pure white 

 but some under wing-coverts especially along edge of wing tipped 

 black-brown ; tail white with broad subterminal black band, 

 reduced (sometimes to a spot) on outer feathers ; primaries like 

 juvenile but blacker and outer webs at base more or less edged 

 whitish-grey, 2nd (outer) with white subterminal spot (varying but 

 usually large) on inner web and sometimes small spot on outer, 3rd 

 with or without white spot on inner web, 7th and 8th pale slate- 

 grey with varying amount of black at tip and down centre and small 

 white apex, 9th to 11th slate-grey tipped white ; secondaries slate- 

 grey tipped white with varying black-brown median streaks ; 

 primary-coverts black tipped white ; wing-coverts slate-grey but 

 those along edge of wing and most lesser coverts tipped brown and 

 sometimes others with brown median streaks. This plumage is 

 acquired by complete moult as in adult. Summer. — After partial 

 moult as in adult head becomes all round mostly black with some 

 white feathers interspersed, back of neck white and rest of upper- 

 parts much as adult but wings and tail as 2nd winter. 



Third winter and summer. — Like adult but with varying number 

 of subterminal black spots or marks on tail ; primaries with more 

 black than in adult, 2nd always with subterminal black bar, 3rd 

 with white at tip confined to spot on inner web, 8th frequently with 

 some black sub terminally. 



Measurements and structure. — $ wing 475-510 mm. (juv. 470- 

 480), tail 170-190, tarsus 75-84, bill from feathers 60-69 (juv. 55-67) 

 (12 measured). ? wing 435-480 (juv. 430-470), bill 49-61 (juv. 48- 

 60). Primaries : 1st very small and narrow, 2nd longest, 3rd as 

 long or 2-7 mm. shorter, 4th 15-30 shorter, 5th 40-55 shorter. 

 Rest of structure, including shape of bill, as in Larus melanocephalus . 



Soft parts. — Bill (ad.) orange -yellow, terminal portion orange- 

 red and broad black subterminal band on both mandibles, (juv. 

 and 1st winter) basal portion grey to pale brownish, subterminal 

 horn-black, tip paler, (2nd winter) apparently like adult ; legs and 

 feet (ad.) greenish-yellow, (juv. and 1st winter) lead-grey to grey- 

 brown ; iris brown ; orbital ring deep red. 



Characters. — No subspecies. Distinguished from other British 

 Gulls by its large size and shape of bill, besides black on head and 

 in juvenile white-margined black secondaries. 



Breeding-habits. — Nests in colonies on low lying sandy spits in 

 salt seas, but also on islands overgrown with high reeds in the great 



