230 A PRACTICAL HANDBOOK OF BRITISH BIRDS. 



have juvenile feathers of upper-parts paler, and wings and tail 

 much paler than in C. cygnus. 



First winter and summer. — Apparently acquires some white 

 feathers on mantle and scapulars, one (<J 14.3.20 coll. E. L. Schioler) 

 has acquired new white mantle and scapulars and innermost 

 secondaries and apparently one new pair of tail-feathers ; rest of 

 plumage as in juvenile. Very little material examined. 



Second winter and summer. — Probably as adult but no material 

 examined. 



Measurements and structure. — £ wing 515-537 mm. (measured 

 with tape, see vol. i, p. *xiii), tail 150-168, tarsus 100-115, middle 

 toe with claw 127-138, bill from feathers 90-98 (8 measured). £ 

 wing 475-525, middle toe with claw 107-137, bill 84-95 (7 measured). 

 Primaries : 1st narrow and more than half longest primary-covert, 

 3rd and 4th about equal and longest, 5th 15-24 shorter, 6th 60-72 

 shorter. Other structure as in C. cygnus. 



Soft parts. — Bill (ad.) base of upper mandible yellow, yellow 

 extending along culmen to below concave depression but laterally 

 not to nostrils ; black line at base of culmen bordering fore-head, in 

 some extending from eye to eye, in some base of culmen entirely 

 black and sides of bill only yellow, in others culmen black with a 

 bridge of yellow above concave depression, rest of bill black, sides 

 of rami of under mandible yellow, intercrural space yellow ; bill 

 (juv.) base of upper mandible to nostrils livid white, culmen 

 mottled pink-brown, yellowish along ridge, tip, nail and edges of 

 upper mandible blackish, intercrural space livid flesh-colour, 

 mottled black along rami ; legs and feet (ad.) black, (juv.) dirty 

 yellowish-white or horny, each scale surrounded greyish-black ; 

 webs on upper surface black mottled white ; iris brown. 



Characters and allied forms. — C. b. jankowshii (E. Siberia) 

 said to be larger with a broader bill. Distinguished from C. cygnus 

 in all plumages by smaller size and yellow at sides of bill not extend- 

 ing to nostrils. 



Breeding-habits. — Breeds on low-lying ground on islands and 

 near mouths of large rivers, close to water. Nest. — Large heap of 

 moss mixed with some mud, and with depression in middle. Eggs. — 

 Probably 4 is normal clutch, but 3 also recorded ; creamy-white 

 but readily stained. Average of 9 authentic eggs, 103.6x67.3. 

 Max.: 109x70. Min. : 99.1 X 65.1 and 101.8x64.6 mm. Breeding- 

 season. — During June. Incubation. — No positive data. Single- 

 brooded. 



Food. — Grasses, clover and aquatic plants ; also part of small fish 

 recorded and water -insects. 



Distribution. — British Isles. — Winter- visitor, Nov., occasional 

 Oct., to March-April. Fairly frequent England and Wales in severe 

 winters, and sometimes abundant Scotland, especially in Hebrides. 



