252 THE ZOOLOGIST. 



their lives,* owing to disease of the ovary, and it is probable 

 that birds in captivity (which certainly live longer, when properly 

 treated, than birds at liberty) are more subject to that disease 

 than when they are free. This would be a more probable 

 solution of the late assumption of the blue-black plumage by 

 Mr. Souef's birds than the conclusion that the Satin Bower-bird 

 only assumed its black clothes to die in. The wedding garments 

 of birds are believed to be assumed for the subjugation of the 

 hens, and birds do not wait until they are old before they begin 

 to breed. 



There is no doubt that albinism in birds is due to con- 

 stitutional weakness, and is a frequent result of close inbreeding. 

 If a pair of Sparrows (Passer domesticus) takes up its quarters in 

 one part of a building, or in the roof of an isolated cottage, the 

 young, inbreeding for successive generations, are pretty certain 

 to throw individuals with more or less white in the plumage. 

 The White Dove (popularly known as " White Java") is known 

 to be merely the albino form of the Collared Turtle (Turtur 

 risorius), and Mr. Abrahams assured me that it could always be 

 produced by close inbreeding from the common type. It is 

 probable that inbreeding first produced the pied Java Sparrows, 

 from which the Chinese, by careful selection, evolved the white 

 variety of that species. White in the plumage of birds is 

 frequently due to old age, and increases year by year. A Chaf- 

 finch which I had for about fifteen years acquired quite white 

 eyelids before its death, and a Cordon-bleu (Estrilda phoenicotis) , 

 now in my possession, began to acquire a white wing-speculum 

 some three or four years ago ; this has now become a large white 

 patch. A pied Chaffinch, which I once caught in the garden, 

 became much whiter at the two succeeding moults ; and a pied 

 Blackbird sent to me a year or more ago showed an increase of 

 white after its autumn moult ; both were delicate birds, and did 

 not live long, so that I conclude they were probably inbred. 



* I had a remarkable instance of this in the case of a Eosa's Parrakeet 

 (Palceornis rosa), which was so persecuted by her own child — a powerful 

 young hen — that I had to cage her up separately. Two years later she 

 assumed full male plumage, and a few months afterwards died. When 

 opened the ovary was found to have almost entirely disappeared, the only 

 remains being two twisted knots on the right side, almost simulating small 

 testes. 



