252 THE SWALLOW. 



turning each time to settle on the aytes or banks of the 

 Thames. When about to take their final departure, they 

 wheel round and round in the air, mounting higher and 

 higher till they can be seen no longer, and but few stragglers 

 are left behind. Swallows fly low on the approach of rain, as 

 probably flies, and other insects, on which they feed, do not 

 rise at such times above the surface of the land or water. 



At a dinner party in London, the conversation turned upon 

 Natural History, and I was much amused with a curious idea 

 respecting Swallows and martins, which proceeded from a 

 gentleman who sat next me. He told me that he had 

 devoted much time and attention to the habits of these birds, 

 having excellent opportunities of doing so, in consequence of 

 their frequenting a particular spot opposite the window of a 

 room in which he usually sat. His idea was, and he appeared 

 to entertain but little doubt of its accuracy, that before Swal- 

 lows and martins migrate, they make a small deposite of flies in 

 a vacuum which may be found under each of the wings of these 

 birds ; and that these flies are fixed there by means of the 

 same sort of glue which is used in working up the mud for 

 their nests. These flies, he supposes, serve the birds for food 

 during their long passage from this country to another. 



It is impossible not to admire its rapid whirls, and long 

 continued flight, dashing as it does, sometimes under the a*rch 

 of a bridge, and at other times round and round a neighboring 

 building, " squeaking as it goes in a very clamorous manner." 

 This is supposed to be the mode in which the male serenades 

 the hen when sitting, and I think there can be little doubt 

 but that such is the case. The squeak is repeated every 

 time the bird passes the entrance of the nest ; and I have 

 observed that at such time its flight perceptibly slackens. 

 The swift keeps on the wing longer, perhaps, than any other 

 bird, never going to roost in the longer days till about a quar- 

 ter before nine. Just before they .retire for the night, their 

 squeak may be heard, and they then dash and shoot about 

 with wonderful rapidity. They are on the wing at least 

 seventeen hours, when the days are at their greatest length. 



