210 A PRACTICAL HANDBOOK OF BRITISH BIRDS. 



some grey feathers mixed with black on nape ; throat black ; chin 

 mixture of black and white ; mantle not so pure a grey as in adult 

 male. 



Nestling. — (Not examined. ) 



Juvenile. — Like that of M. a. lugiihris and difficult to distinguish 

 from it, but usually rather paler on upper-parts and with no black 

 on fore-head. 



First winter. Male. — Like adult female but usually with 

 rather more black on crown. The juvenile body-feathers, lesser 

 wing-coverts, most median and inner greater coverts and some 

 inner secondaries are moulted in Aug. -Sept., but not rest of wings 

 or tail. Su7nmer. — Moult as adult but many greater and median 

 wing-coverts appear to be always moulted, as well as central 

 pair of tail-feathers and occasionally whole tail. Like adult summer 

 male except that wing-feathers are considerably more browai. 



First winter. Female. — Like adult female in winter but 

 fore-head very rarely with any white showing, almost alwaj's 

 entirel}' grey washed olivaceous ; crown grey with no black and 

 usually tinged olivaceous. Moult as in first winter male. Summer. 

 — Moult as in first summer male. Like adult female summer 

 but fore-head less white and chin with more white and crown 

 sometimes with more grey, wing-feathers bro^vl^. 



Measurements and structure. — ^ wing 87-96 mm., tail 85-93, 

 tarsus 23.5-26, bill from skull 13-15 (12 measured). $ wing 81-89. 

 Averages slightly larger than M. a. lugubris. Structure as that 

 form. 



Soft parts. — Bill, legs and feet black ; iris brown-black. 



Characters and allied forms. — Distinguished from adult and 

 first summer male and female M. a. lugubris b}^ the absence of 

 black on mantle ; but first summer female lugubris often has 

 scarcely any black on mantle and is then difficult to distinguish 

 from adult summer female alba, which, however, has paler grey 

 mantle and less black on rump ; adult male alba very similar to 

 first winter lugubris but mantle al^^ays paler and purer grey, but 

 some examples are difficult to distinguish even when in hand ; 

 female winter and male first winter alba distinguishable from all 

 plumages of lugubris by absence, or slight amomit, of black on 

 crown and usually grey (not white) fore-head, but mantle, although 

 usually paler than first winter lugubris, is sometimes as dull a grey 

 and like those examples of first winter female lugubris which have 

 no black in mantle. M. a. dukhunensis (west Siberia, Caucasus), 

 resembles M. a. alba, but has paler ujaper-parts and more white 

 on greater and median wing-coverts, M. a. baicalensis (middle 

 east Siberia) is similar but has Avhite chin in summer, M. a. leucopsis 

 (Manchuria, Mongolia, north-west China, Tibet) has upper-parts 

 much like M. a. lugubris but greater and median wing-coverts 

 with much white, and chin white in summer, M. a. ocularis (north- 



