HUMMING-BIRDS 



we find them all pointing in the same direction. The sternum 

 or breastbone is not notched behind ; and this agrees with the 

 swifts, and not with the sun-birds, whose sternum has two deep 

 notches behind, as in all the families of the vast order of 

 Passeres to which the latter belong. The eggs of both swifts 

 and humming-birds are white, only two in number, and 

 resembling each other in texture. And in the arrangement 

 of the feather-tracts the humming-birds approach more nearly 

 to the swifts than they do to any other birds ; and altogether 

 differ from the sun-birds, which in this respect, as in so many 

 others, resemble the honey-suckers of Australia and other true 

 passerine birds. 



Resemblances of Swifts and Humming-birds 

 Having this clue to their affinities, we shall find other 

 peculiarities common to these two groups, the swifts and the 

 humming-birds. They have both ten tail-feathers, while the 

 sun-birds have twelve. They have both only sixteen true 

 quill-feathers, and they are the only birds which have so 

 small a number. The humming-birds are remarkable for 

 having, in almost all the species, the first quill the longest of 

 all, the only other birds resembling them in this respect 

 being a few species of swifts ; and, lastly, in both groups 

 the plumage is remarkably compact and closely pressed to 

 the body. Yet, with all these points of agreement, we find 

 an extreme diversity in the bills and tongues of the two 

 groups. The swifts have a short, broad, flat bill, with a flat 

 horny -tipped tongue of the usual character; while the 

 humming-birds have a very long, narrow, almost cylindrical 

 bill, containing a tubular and highly extensible tongue. The 

 essential point, however, is, that whereas hardly any of the 

 other characters we have adduced are adaptive, or strictly 

 correlated with habits and economy, this character is pre- 

 eminently so ; for the swifts are pure aerial insect-hunters, 

 and their short, broad bills and wide gape are essential to 

 their mode of life. The humming-birds, on the other hand, 

 are floral insect-hunters, and for this purpose their peculiarly 

 long bills and extensile tongues are especially adapted ; while 

 they are at the same time honey-suckers, and for this purpose 

 have acquired the tubular tongue. The formation of such a 



