Mutations among Birds 



A well-marked mutation which appears regu- 

 larly in nature is the red-headed variety of the 

 beautiful Gouldian Finch (Poephila mirabilis) 

 of North Australia. Normally the head of the 

 cock is black, but in about ten per cent, of the 

 individuals the cock has a crimson head, while 

 that of the hen is dull crimson and black. 



Mutations which occur with such regularity 

 are certainly rare. On the other hand, there are 

 certain mutations which we may expect to see 

 appear in any species of plant or animal. 



Albinistic forms are a case in point, and less 

 frequently we see white varieties which are not 

 pure albinos, because the eye retains some at 

 least of the normal pigment. As examples, we 

 may cite white dogs, cats, fowls, horses, ducks, 

 geese, and Java sparrows among domesticated 

 animals, and the white forms of the Amazonian 

 dolphin and of the giant Petrel of the South 

 seas (Ossifraga gigantea] among wild creatures. 



In a white mutation the eye may lose all its 

 pigment, and then we have a true albino. Such 

 forms on account of their imperfect vision cannot 

 survive in a state of nature, hence no wild pink- 

 eyed species are known. 



Or the eye may display a partial loss of pig- 

 ment, as, for example, in the white domestic 

 forms of the common goose, the Chinese goose, 

 and the Muscovy duck. Finn saw a case in 

 which the eyes of a pink-eyed rabbit changed 



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