bewick's swan. 229 



Characters.— No subspecies. Distinguished from other British 

 Swans by large size and colouring of bill. 



Breeding-habits. — Breeds on islands in lakes, or drier patches in 

 swamps. Nest. — Large heap of mosses and marsh-plants partly 

 solidified with earth and with depression in middle. Remains of old 

 nests visible for years after they have ceased to be used. Eggs. — 

 4-6, rarely 7, yellowish-white when first laid, but soon becoming 

 nest-stained. Average of 75 eggs, 112.8x72.6. Max.: 126.3 X 

 71.3 and 114x77.4. Min. : 105.2x72 and 117 X 68.1 mm. Breeding- 

 season. — Usually late May or early June in Iceland ; exceptionally 

 early May. Incubation. — By female alone. Period 40 days (Faber) ; 

 in captivity 31 and 42 days. Single-brooded. 



Food. — Chiefly vegetable ; grass, clover and roots and stems of 

 water-weeds. In summer also fresh-water mollusca, worms and 

 aquatic insects. 



Distribution. — British Isles. — Winter -visitor (Oct. -No v. to March- 

 April, occasionally May and June). More frequent Scotland than 

 England, rare Ireland. More abundant severe weather. Used to 

 breed Orkneys. Reported to have bred west Perths. 1919 and 

 probably 1918 (E. H. Place, Field, Ap. 17, 1920) and two adults 

 summer 1919 visited Loch Trieg (W. E. Clarke, Scot. Nat., 1919, 

 p. 196, 1920, p. 68). Pinioned birds have bred since 1910 Shetland 

 (cf. Ann. Scot. N.H., 1910, p. 245). 



Distribution. — Abroad. — Iceland, north Europe and north Asia, 

 migrating southwards to central and south Europe, rarely N. 

 Africa, central Asia, Persia, China, and occasionally Japan. Occa- 

 sional in Greenland. 



CYGNUS BEWICKII 



286. Cygnus bewickii bewickii Yarr.— BEWICK'S SWAN. 



Cygnus Bewickii Yarrell, Trans. Linn. Soc. London, xvi, ii, p. 453 



(1830— England). 



Cygnus bewicki Yarrell, Yarrell, iv, p. 315 ; Saunders, p. 415. 



Description (Plate 5). — Adult male and female. Winter and 

 summer. — Entire plumage white, feathers of head and under-parts 

 in some with rusty stain on edgings. This plumage is apparently 

 acquired by a complete moult ; one (ad. $ Novaya Zemlia, Sept. 1st, 

 1902, in Tring Mus.) has remiges of both wings in quill, and is in full 

 moult on upper- but not under-parts, one (ad. $ Jan. 13th) is 

 moulting body-feathers ; very little moulting material examined. 



Nestling. — Like nestling C. cygnus, but apparently loral down, 

 though extending slightly further than frontal down, does not 

 extend so far on to bill as in C. cygnus : down not extending so far 

 on to intercrural space as in C. cygnus and not produced to such a 

 sharp point at tip. 



Juvenile. — None in fresh plumage examined. Two (March) 



