736 A PRACTICAL HANDBOOK OF BRITISH BIRDS. 



a line of varying width along shaft on inner web, rest of inner web 

 and shaft white, 3rd same but wider black border to inner edge of 

 inner web and outer web with some white at base, 4th with longer 

 black tip (small white spot at apex), black extending along outer 

 edge of outer web for about half its length, basal half of outer web 

 white, black border to inner web broader and greyer, 5th same, but 

 with little or no white on inner web, rest same but outer webs grey 

 (that of 6th whitish-grey) and inner webs, proximal to black tips, 

 grey-black ; secondaries grey-black with grey bases, edges and 

 tips, inner feathers with grey-black restricted to median patch near 

 tip, innermost dark brown tipped pale buff as scapulars ; primary- 

 coverts white with varying amount of black along shaft, inner 

 feathers with grey outer webs, black-brown inner webs and buffish 

 tips ; greater coverts grey, tipped buff and usually with some 

 dusky-brown shaft-streaks, innermost feathers and median and 

 lesser coverts dark brown with grey bases and pale buff tips, but 

 feathers along edge and bend of wing white and upper series of 

 lesser coverts mostly blue-grey with varying amount of dark 

 brown in centres. 



First winter. — Body-plumage like adult winter but sometimes 

 a few juvenile scapulars and a few other feathers are not moulted, 

 tail and wing -feathers as juvenile but sometimes some lesser, median 

 or inner greater coverts new and like adult. The juvenile body- 

 plumage and sometimes some wing-coverts (often none) are moulted 

 July to Dec, but not tail- and wing -feathers, nor rest of wing-coverts. 

 First summer. — A moult of body-feathers and some innermost 

 wing-coverts takes place Jan. to May, but not rest of wing-coverts, 

 nor wing -feathers, nor tail (occasionally central pair is moulted). 

 New feathers as adult summer but head usually with varying amount 

 of white mixed with brown, and fore-head, lores and chin sometimes 

 mostly white ; back of neck not so white as adult ; wing-coverts 

 as 1st winter but showing more grey owing to wear of tips. N.B. — 

 Very few first summer birds available for examination. 



Second winter and summer. — As adults but two birds, which had 

 been " ringed," had in 2nd winter fine black shaft-streaks to outer 

 primary-coverts and probably other similar birds are in 2nd winter 

 or summer. 



Measurements and structure. — $ wing 295-315 (one 320) mm., 

 tail 110-125, tarsus 43-49, bill from feathers 31-36 (14 British 

 measured). $ wing 285-302, bill 29-33. Primaries : 1st narrow, 

 pointed and about two-thirds primary-coverts, 2nd longest, 3rd as 

 long or 2-5 mm. shorter, 4th 13-23 shorter, 5th 34-47 shorter. Rest 

 of structure as Bonaparte's Gull. 



Soft parts. — (Ad.) bill, legs, and feet and edges of eyelid 

 crimson ; (juv. and 1st winter) bill dull orange to dull flesh, tip 

 blackish, legs and feet yellow-flesh, webs and joints dusky ; iris 

 brown. 



Characters and allied forms. — L. r. sibiricus (Kamtschatka) 



