THE WANDERING ALBATROSS 269 



natural selection, not only in birds, but also in insects. It is 

 evident that in an equable climate, where the exact time of 

 breeding was not very important, many variations might be 

 preserved by this means ; while in more rigorous climates, where 

 the breeding-season must necessarily be short, this kind of 

 physiological isolation could not occur. And this may account 

 for the greater number of species in tropical countries, especially 

 on islands, as contrasted with the enormous number of 

 individuals belonging to very few species, which is characteristic 

 of temperate regions with continental climates. 



Key to the Genera, 



1. Tail pointed at the end. Phoebetr|a. 

 Tail rounded at the end. 2 



2. Anterior margin of under surface of wing white. Diouiedea. 

 Anterior margin of under surface of wing dark. Thalassarche. 



Genus Diomedea. 



Large. The back white or brown. Tail short and rounded. 

 Southern Ocean and North Pacific. 



Key to the Species. 



1. Upper back with transverse black lines. D. exulans. 

 Upper back without transverse black lines. 2 



2. Wing coverts dark grey and white. D. regia. 

 Wing coverts nearly white. D. chionoptera. 



The Wandering Albatross.— Toroa. 



Diomedea extdans. 



White. The back transversely pencilled with black. Quills, black. 

 Eyelids, pale purple. Bill, flesh colour (horn colour when dry). Legs and 

 feet flesh colour. Length of the wing, 25.5 in.; of the tarsus, 4.8 in. 

 Egg — About 5 in. in length. Young, chocolate brown, with a white face. 

 Under wings coverts and axillaries, white. Southern Ocean. Breeds 

 on Adams Island, Auckland Group, and at the Antipodes. Its range 

 extends through the Southern Pacific Ocean to within about 600 miles of 

 Cape Horn, after which it appears to be replaced by the snowy albatross 

 (Z). chionoptera) . 



The albatross takes three or four years to attain the adult 

 plumage. The first year is spent in the nest; after leaving it 

 the young bird becomes gradually white, first on the abdomen, 



