128 BRITAIN'S BIRDS AND THEIR NESTS. 



In starting a new variety the breeder takes advantage 

 of some already inherent character. Without this he 

 cannot get a beginning. Given this, however, he can 

 produce, by the mating of carefully selected birds from 

 generation to generation, a fairly distinct race in a time 

 which seems insignificant when compared with the slow 

 march of natural evolution. Under natural conditions, a 

 characteristic may have to give its possessor some advantage 

 over other individuals if it is to be perpetuated and 

 increased. The elimination of the less - favoured birds 

 may be a very slow process, repeated at every step ; but 

 imder domestication elimination is instantaneous, and 

 merely in accordance with the breeder's will. 



The differences between such races are perhaps not so 

 important and fundamental as they might at first sight 

 appear. Certainly they lack permanence, and a breed 

 may be lost as rapidly as it was built up ; a few 

 generations of indiscriminate mating destroy the effects 

 of selection. In the case of two birds of different 

 breeds, the chief quality in common is the underlying 

 ancestral strain, however disguised. This has probably 

 the best chance, and the offspring may show a ' throw- 

 back ' towards the original stock, with its more enduring 

 characteristics. Thus it is a familiar fact that the majority 

 of domestic Pigeons, left more or less to shift for 

 themselves, closely resemble true wild Rock-Doves. But 

 albinos and other marked variations occur with much 

 greater frequency among the former than the latter. 



It is sometimes difficult to distinguish between truly 

 wild and merely ' feral ' Rock-Pigeons. ' Feral ' is the 

 term for domestic animals that have reverted to the 

 ' wild ' state. The term ' wild "* is strictly applicable 

 only to birds whose ancestors have never been under 

 domestication. 



