50 COLIN CLOUT'S CALENDAR. 



humming-birds and swallows ; but he reassured himself 

 when he looked at the general external likeness of the 

 two tropical groups. Now, however, we have learned 

 that such external likenesses are necessarily produced 

 by community of habit and mode of life ; while under- 

 lying structural resemblance forms the best test of 

 genealogical relationship. Mr. Wallace has shown con- 

 clusively that the humming-birds are in reality modified 

 swifts, and that their resemblance to the Oriental sun- 

 birds is wholly due to the similarity of their circum- 

 stances. 



In fact, the habits of the two races, though much 

 alike in many respects, still bear evident traces of their 

 original derivation. The sun-birds are by origin creepers ; 

 and, like other creepers, they have not very large or 

 powerful wings, and their feet are formed for perching", 

 which is not the case with either the swifts or the hum- 

 ming-birds. When a sun-bird wants to suck the honey 

 of a flower, it does not hover in front of it, poised upon 

 swiftly vibrating pinions, like its supposed American 

 allies ; but it perches first upon the stalk or branch, and 

 then extracts the nectar at its ease. The humming- 

 birds, on the other hand, being developed insect-eaters, 

 never alight, but catch their food upon the wing, just 

 as their ancestors the swifts were accustomed to do. 

 Moreover, they are not to any great extent honey- 

 suckers ; what they seek in the nectary is not so much 

 the honey as the insects which have come to eat it. 

 These they can extract with their long tongues at a 

 single flick, and then they dart away again, just like the 

 swallows, in search of more. Mr. Wallace has shown 

 that young humming-birds starve upon honey, but live 



