MUTE SWAN. 



479 



obtained in this country in an apparently wild state have probably been 

 escaped birds. It appears to me that the so-called Polish Swan can only 

 be regarded as a quasi-albino produced by domestication, probably from the 

 same causes that have originated the white varieties of the domestic Dnck 

 and the Goose. The size of the frontal tubercle is principally a question 

 of age ; the difference in colour of the bill of the two forms seems to have 

 been greatly exaggerated, and many examples of the Hooper in first 

 plumage fade into almost white by the abrasion of the grey tips of the 

 feathers. 



MUTE SWAN. 



