92 



BRITISH SWANS. 

 PLATE II. * 



IN the accompanying plate we have endeavoured to 

 shew the principal external distinctions of the four 

 species of swans which occasionally visit this country. 

 The plumage of all of them is so similar, that with- 

 out noticing the differences of the bill and head, or 

 comparing the structure of the trachea and its con- 

 volutions, there is great difficulty in distinguishing 

 them. 



THE MUTE OR TAME SWAN, 



Cygnus olar, 

 PLATE II.* FIG. 2, 



Is easily distinguished from the Hooper, or Bewick's 

 Swan, by the distribution of the colours on the 

 bill. In the two last the apical half of the bill is 

 black, the base yellow in different proportions, 

 while in the domesticated bird the reverse is the 

 case, the bill being of a rich reddish orange, the 

 nail, base, space between the eye, and tubercle or 

 knob, black ; internally the trachea is simple, and 

 enters directly into the cavity of the body, conse- 

 quently the sternum has no hollow in its keel for 

 its reception. 



