THE COMMON SCOTER. 371 



body, flanks and under tail-coverts, sometimes some feathers of 

 rest of under-parts and sometimes some tail-feathers are moulted 

 from Dec. onwards. Amount of black plumage acquired varies 

 considerably individually. 



First eclipse. Male. — (Not examined.) 



Second winter and summer. Male. — Apparently as adult male 

 but birds with under-parts browner than others may possibly be 

 2nd year males. 



First winter and summer. Female. — Moult as in male. New 

 body-feathers as adult female, new tail-feathers narrower, wing as 

 juvenile. 



Measurements and structure. — $ wing 228-242 mm., tail 80- 

 100, tarsus 40.5-43, bill from feathers 45-49 (12 measured). $ wing 

 220-229, bill 42-46. Primaries : 1st narrow, pointed and less than 

 half longest primary- covert, 3rd longest, 4th equal or 2-4 mm. 

 shorter, 2nd 6-10 shorter, 5th 11-15 shorter, 6th 25-30 shorter. 

 Emargination : ad. ^, 2nd deeply emarginated inner web, 3rd very 

 slightly both webs ; ad. $, 2nd not nearly so deeply as in <$, 3rd very 

 slightly outer web ; juv. <£, 2nd emarginated but not deeply as in 

 ad. $, narrower and more tapering towards point than in ad. $ ; 

 juv. 5, 2nd hardly distinguishable from that of ad. $. Innermost 

 secondaries tapering to a point and longest shorter than 4th to 6th 

 primaries. Scapulars more or less pointed at tip. Tail graduated 

 and acuminate, 16 stiff, pointed feathers, central pair longest. Bill 

 nearly as long as head, higher than broad at base, depressed and 

 flattened towards tip which is rounded ; upper mandible in ad. <$ 

 with well-developed knob usually absent in female and juvenile 

 but in some females more or less developed ; in forward young 

 males developed by April ; nail large and broadly elliptical. 

 Feathers at base of bill form a nearly straight oblique line from 

 fore-head to rictus advancing scarcely if at all on fore-head. Round 

 base of upper -mandible in ad. $ a curious band of short down-like 

 feathers. 



Soft parts. — Bill (ad. ^) black, middle portion between and 

 around nostrils from knob to nail yellow or orange, (ad. $) greenish- 

 black (in some with a narrow band between nostrils extending almost 

 to nail orange -yellow) and nostril openings yellow, (juv. <^)* black 

 with only a slight touch of reddish -yellow round nostrils (Millais), 

 (juv. $) lead-coloured ; legs and feet (ad. ^) brown-black, webs 

 blackish, (ad. $) olive -brown, webs blackish ; iris brown. 



Characters and allied forms. — Adult male of 0. n. americana 

 (N. America) has nail arched and decidedly hooked and colour of 

 bill different, females and immature males have nail more convex 

 than in 0. n. nigra (less marked in very young birds), adult female 

 with small yellow patch on culmen between nostrils. Uniform 



* Some young males by Jan. have ridge of culmen almost to nail and 

 area round nostrils yellow. 



