478 BRITISH BIRDS. 



spring, possibly from their winter-quarters in the Mediterranean. Occasion- 

 ally other pairs arrive and attempt to seize the old nests, when a battle 

 royal takes place. These fights are sometimes so furious that the white 

 plumage of the Swans becomes stained with blood. The half-tame Swans 

 which breed on the broads in Norfolk build similar nests, generally on an 

 island, and often under the shelter of a willow, but it is said that they 

 build a fresh nest every season. Wild Swans seldom have eggs before May, 

 but tame Swans often breed much earlier, and may be seen sitting on their 

 eggs when the ground is covered with snow. Naumann says that incuba- 

 tion lasts from 36 to 39 days. The number of eggs varies from five to 

 eight. There is often very little difference in the shape of the two ends ; 

 the texture is rough, and there is scarcely any gloss. They vary in length 

 from 4'9 to 4'3 inch, and in breadth from 3'1 to 2'8 inch. They may 

 always be distinguished from eggs of the other British Swans by their 

 greenish- white colour. 



Compared with the Hooper Swan the Mute Swan is a silent bird, but 

 when angry it hisses like a goose, and in pairing-time it has a few low not 

 unmusical notes. Both the elder and the younger Naumann state that 

 this Swan in a wild state at its breeding-grounds has a loud trumpet-like 

 note, like that of the Crane or the Hooper. 



The adult Mute Swan has the entire plumage pure white. The lores, 

 frontal tubercle, the base of the upper mandible, the nostrils, the nail, the 

 edges of the upper mandible, and the whole of the under mandible black, 

 remainder reddish orange ; legs and feet dull black ; irides hazel. Young 

 in first plumage are almost uniform greyish brown, the feathers being 

 white with brown tips, which gradually abrade to almost white in the course 

 of the following spring and summer. Bill greyish black, the frontal 

 tubercle only slightly indicated; legs and feet pale lead-colour. After 

 their first moult (when they are about a year old) the fully adult plumage 

 is assumed, the only signs of immaturity being the smaller frontal tubercle 

 and the replacement of the orange-red portion of the bill by flesh-colour. 



As long ago as 1838 Yarrell described what he regarded as a new species 

 of Swan (Proc. Zool. Soc. 1838, p. 19), under the name of Cygnus immuta- 

 bilis. It was supposed to differ from the common species in having when 

 adult a smaller knob at the base of the bill, slate-grey instead of black 

 legs, arid when young in having the bill flesh-colour instead of greyish 

 black, and the plumage of the upper parts pure white without brown ends 

 to the feathei s , It has been called the Polish Swan under the mistaken 

 impression that it was a native of that country. As a matter of fact it 

 appears to be confined to the British Islands, the only instance of its having 

 occurred elsewhere being a single example obtained on the Lake of Haar- 

 lem, in Holland, in December 1840. It has never been known to breed 

 except in a state of domestication, and the few examples which have been 



