4(i7 



ON THE EXCITING CAUSES OF VARIETIES IN BIRDS AND 

 OTHER ANIMALS. 



By Neville Wood, Esq. 



In various numbers of The Naturalist, correspondents have recorded instances 

 of varieties in birds and other animals which have fallen under their observation, 

 or come to their knowledge. In the present paper we propose briefly to explain 

 our views respecting the exciting causes of these curious modifications. 



The Common Fowl (Gallus domesticus, Auct., Phasianus gallus, Linn.), 

 originally derived from Asia, is now scarcely known in its native haunts ; but 

 has long been extensively cultivated as a domestic bird in almost every country. 

 What influence may be drawn from these facts ? Now we are of opinion, that, 

 ceteris paribus, the more thoroughly and the longer any animal is domesticated, 

 and the more the domesticated differs from the wild state, the more subject will 

 that animal be to variety, and the more remarkable will the varieties be. Both 

 arguments and facts fully support this theory ; and what we at first considered a 

 mere hypothesis, has at length ripened into a matter of demonstration. 



Thus, varieties of birds inhabiting extensive tracts of fen-land, wide and arid 

 plains, or the summits of bleak mountains, little frequented by Man, are seldom 

 noticed, because they rarely occur. The ordinary changes of plumage, termed 

 moulting, there take place with almost unerring regularity, as, for instance, in 

 the various Ptarmigans of the hill-top, the Waders ( Grattatores) of the moist 

 and sedgy river-side, the Petrels, Ducks, and Gulls of the " wild unbounded 

 sea," &c. All these, and many others, live strictly according to their nature. 



A second class furnishes the collecting naturalist with occasional varieties. 

 Thus the Wild Duck ( Anas boschas, Linn.), which abounds throughout the year 

 in the fresh waters of Britain, is necessarily partially, though but little, under 

 the jurisdiction of Man. Varieties are accordingly occasionally met with, from 

 the dark rich colour of the natural state to a chocolate hue, or even pure white. 

 The Partridge belongs to the same division, and yields an occasional variety. 

 The Pheasant and the House Sparrow depend still more upon our bounty and 

 our works, and hence varieties are tolerably frequent in these species, though not 

 very much so, considering the great abundance of these birds in almost every part 

 of the country. Sparrows occur black, white, and cream-coloured, and the 

 varieties of the Pheasant — an imported species, and half domesticated — are still 

 more frequent and diverse. 



Lastly, we come to the wholly-domesticated races of birds. In the two 

 former classes the varieties form the exceptions to a general rule ; but here the 



