103 



have seen, have become almost perfectly adapted to the life which they 

 have chosen. But apparently they had not taken up the whole ground, 

 for in the course of time there appears another family radically different 

 in structure and belonging to a much higher order, the Passeres. It 

 covets the food of the swifts, which can be taken only in one way — on 

 the wing, as those birds take it ; so it adopts their manner of life, and 

 in time, without losing its passerine characteristics, the swallow becomes 

 superficially so like the swift that to the casual observer they are both 

 as one. Not only does the resemblance of these families cover the gen- 

 eral colour of the plumage, the shape and proportion of the wings and 

 consequent style of flight, the form of head and wide-gaping mouth, 

 adapted for scooping in the fluttering prey, but even the voices of the 

 two, in spite of the great difference in the structure of the syrinx, are 

 really so much alike as to be easily confounded. A still more interesting 

 point of similarity is seen in the way both the swift and the swallow 

 have changed their manner of nesting to suit the change caused by the 

 advent of civilized man. As long as this continent was under the 

 domain of the red man the chimney swift, as has been shown, found a 

 place both for roosting and nesting in a hollow tree, closed at the 

 bottom and with a narrow opening at the top. The barn and cliff 

 swallows fastened their castles of mud and straw against a lofty rock, 

 while the purple martin and the white-belly nested in crevices of the 

 rock or in deserted woodpecker-holes in the trees. The white man 

 came upon the scene, and long before his progress had cleared away, 

 even, any large fraction of the forest, the switt had found out the sup- 

 erior advantages of protection and stability afforded by an empty 

 chimney; for even Wilson at the beginning of the century knew the 

 bird only as the chimney swift and spoke of the hollow-tree habit as a 

 thing then long passed away. The barn swallow and the martin were 

 almost as prompt in seeking the shelter offered by the outbuildings of 

 the farmer ; and now the cliff swallow, the white-belly and the rough' 

 wing, though a little behind, are fast following the example. The bank 

 swallow alone still clings to the home of his fathers, a burrow in the 

 side of a bank of sand or gravel. The tunnelling out of such a nesting 

 place must often involve heavy labour. Perhaps those little feet of his, 

 feeble as they look, have retained something of the strength of his pas- 



A' 



