THE FOOD OF WILDFOWL. 315 



further to the northward seals up the waters with 

 iron bonds, and as these again become released by 

 the advent of spring, they forthwith return to their 

 former haunts, once more following the opening waters 

 to their nesting grounds in the frozen north. More- 

 over most of these wildfowl, as for instance various 

 kinds of ducks, geese, swans, etc., are in general easily 

 domesticated, and many of them will live, thrive, and 

 reproduce their species in confinement under the fostering 

 care of man. Their food also for the most part con- 

 sists of things that can be easily supplied by man; 

 such as the various kinds of grain, and refuse matters, 

 as well as herbage of the fields, aquatic plants, insects, 

 and fish; whereas that of the migratory swallow pro- 

 bably consists almost entirely of minute winged insects 

 which float at various altitudes in the atmosphere, and 

 are taken by these birds as they dart to and fro upon 

 the wing, and it is probable that the infinite twistings 

 and turnings observable in their flight are occasioned 

 by their pursuit of these insects. In fact there can 

 be no doubt that this is so. 



There are some few classes of birds which shun the 

 neighbourhood of human settlements ; and like the 

 large game animals seem to retire before the advance 

 of the dread tyrant, man. We might instance the 

 bittern in our own country and perhaps a few others, 

 as types of these. * But birds, for the most part, though 

 careful to keep a respectful distance between them- 

 selves and danger, generally seem to regard the sight 

 and sound of human occupancy with comparative 



* Among foreign birds, the wild turkey, the American passenger 

 pigeon, the ruffled grouse, the spruce partridge, the capercailzie, the 

 bustard, and many others. 



