THE LONDON DAW 65 



or partly white blackbirds in London ; but 

 during the same period I have not seen nor 

 heard of a white thrush, and have only seen one 

 white sparrow. My belief is that the species 

 most commonly found with white or partly 

 white plumage are the blackbird, rook, and 

 daw. When carrion crows and ravens were 

 abundant in this country it was probably no 

 very unusual thing to meet with white specimens. 

 The old ornithologist, Willughby, writing over 

 two centuries ago, mentions two milk-white 

 ravens which he saw ; but the fact of their 

 whiteness is less interesting to read at this 

 distant date than the old author's delightful 

 speculations as to the cause of the phenomenon. 

 He doubts that white ravens were as common 

 in this country as Aldrovandus had affirmed 

 that they were, and then adds : ' I rather think 

 that they are found in those mountainous 

 Northern Countries, which are for the greatest 

 part of the year covered with snow : Where also 

 many other Animals change their native colours, 

 and become white, as Bears, Foxes, Blackhircl^, 

 &c., whether it proceeds from the force of imagi- 

 nation, heightened by the constant intuition of 

 Snow, or from the cold of the Climate, occasion- 



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