The Birds of an Eastern Voyage 



bright yellow legs and orange eyelids, than our 

 somewhat anaemic - looking species. Authors 

 call it a "climatic race," but when it bred, as 

 it frequently did, in the gull-pond in our Zoo- 

 logical Gardens, the young birds, when adult, 

 were true to type, in spite of captivity under 

 an alien sky. 



The fact is, "climatic race" is a very mis- 

 leading term ; birds from southern localities are 

 often richer in colour than their representatives 

 in colder lands, but sometimes the different types 

 may occur in the same locality. Thus, in the 

 case of the above - mentioned widely - ranging 

 lesser black-back, the colour of the black wings 

 may vary from a real black to quite a light 

 slate colour, and the extreme forms are found 

 both in the North Atlantic and the south of 

 the Red Sea. The explanation is probably 

 simple enough ; in certain forms a dark or 

 light coloration is correlated with constitutional 

 peculiarities which are suited to certain environ- 

 ment, and hence two species arise in different 

 parts of the bird's range, while in others this 

 is not the case, and the extremes can continue 

 to exist side by side, although a change in 

 the conditions might result in the disappearance 

 of one variety. Climate, of course, may be the 

 determining factor in some cases, but food and 

 the disposition — courage or intelligence — of the 



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