244 CHELIDONES. 



for their few hours, deposit their eggs and die, making the 

 shores and shallows which are inaccessible even by the min- 

 now rank with their innumerable carcases, we feel how much 

 the swallow contributes to keep sweet and clean those waters 

 over which it glides, quaffing or bathing the while. The 

 air, too, is so still, that we hear the repeated strokes of its 

 bill as it captures those insects which, to our sight, are 

 viewless. 



Though many swallows often build in the same locality if 

 there is abundance of food in the vicinity, the finding of their 

 food and that of their broods, every morsel of which is very 

 small and purchased by a laborious flight, leaves them little 

 time for associating with each other, as do many of those 

 birds which find their food in larger portions and with less 

 labour ; and as the young must be fed by the parents for a 

 longer time than is necessary in the case of birds that are not 

 called upon to make so great exertions, the labours of the 

 swallows are thereby further protracted. When, however, 

 the last brood are on the wing, and each has nothing to do 

 but procure its own food, they do assemble together, some- 

 times in very numerous flocks, over meadows on the banks 

 of streams; and they also roost upon the tops of houses and 

 churches, preparatory to their final departure. As the swal- 

 lows spend their active powers chiefly over the waters, while 

 they are in the northern and temperate regions, the old story 

 was, that they spent their winters at the bottom of the 

 same ; but that is, of course, not true : indeed it is impossible, 

 utterly inconsistent with the spring moult of the birds, and 

 even with their existence. If a swallow remained but for a 

 few seconds under water, it could not be brought out alive. 

 The air is their element and that too more exclusively 

 than it is the element of any other birds ; at least, of any 

 that are common in this country. One of the swallow tribe 

 is rarely seen resting on a solid perch, unless by its nest, 



