the scaup-duck:. 329 



One March and one April moulting innermost secondaries. Birds 

 in moult occur from Sept. to April, some acquire a first winter 

 plumage by Jan., others have few new feathers by this date and 

 probably in spring commence to moult straight into first summer 

 plumage or if they only acquire first winter plumage by March 

 probably do not acquire any summer plumage. 



Measurements and structure.' — <J wing 220-230 mm., tail 50-63, 

 tarsus 35-38, bill from feathers 43-47 (12 measured). ? wing 210- 

 220, bill 41-46. Primaries : 1st narrow, pointed and about half 

 longest primary-covert, 2nd longest, 3rd equal or 2-3 mm. shorter, 

 4th 7-10 shorter, 5th 20-22 shorter, 6th 32-38 shorter. Bill about 

 as long as head, as high as broad at base but becoming depressed 

 and broadening to tip which is semi -circular, culmen sloping gradu- 

 ally to tip, scarcely concave, nail small and decurved. Other struc- 

 ture as in N. f. ferina. 



Soft parts. — Bill (ad.) lead-blue, slightly darker in female ; legs 

 and feet (ad.) lead-blue, duller in female ; iris rich golden-yellow. 



Characters and allied forms. — N. m. mariloides (China and 

 Japan) is smaller and male has coarser vermiculations on upper - 

 parts ; N. m. nearctica (N. America) is larger. N. affinis (N. 

 America) is smaller. Vermiculated upper-parts and white speculum 

 distinguish Scaup in all plumages from other British Nyroca but 

 for distinction of those juvenile females with no vermiculations on 

 upper-parts, see Tufted Duck under " characters ". 



Field -characters. — At distance drake might be mistaken for 

 Tufted Drake, especially as crest of latter is not always visible, but 

 Scaup has back much lighter. Duck often difficult to distinguish 

 from female Surf -Scoter, white spots on latter 's face being easily 

 mistaken at distance for a white band round base of bill, which would 

 denote female Scaup. Female and immature Tufted also have some 

 white at base of bill, but not a clearly defined band as in female Scaup. 

 In flocks, usually 7-25 individuals and associates freely with other 

 species. Very silent during winter. Dives in 2-3 fathoms. Usual 

 duration of dive 25-30 seconds. (C. E. Alford.) 



Breeding -habits. — Sociable where found commonly ; many pairs 

 breeding close together. Nest, — Sometimes mere hollow lined with 

 grasses and down (feathers from nest, see Brit. Birds, n, PL 2) ; at 

 times conspicuous or sheltered by tussock of grass or heather and 

 near water. Eggs. — 7 or 8 to 11, but 19 and even 22 have been 

 found in one nest, olive-grey in colour. Average of 100 eggs, 61.7 X 

 43.6. Max.: 68.1 X 44.7 and 59x48. Min. : 54.5x41.5 and 66.3 

 X40.7 mm. Breeding -season. — From end May through June. In- 

 cubation. — By female alone. Period said to be four weeks. Single 

 brooded, 



Food. — Almost entirely animal, but buds and seeds of water-plants 

 are eaten in summer, and Zostera has been recorded, as well as 

 algse, which are brought to the surface for eating. Staple food. 



