154 NATURAL HISTORY OF SELBORNE. 



their heads out at the orifice, where the dams, by clinging 

 to the nest, supply them with food from morning to night. 

 For a time the young are fed on the wing by their parents ; 

 but the feat is done by so quick and almost imperceptible 

 a flight that a person must have attended very exactly to 

 their motions before he would be able to perceive it. As 

 soon as the young are able to shift for themselves, the 

 dams immediately turn their thoughts to the business of a 

 second brood ; while the first flight, shaken ofi" and rejected 

 by their nurses, congregate in great flocks, and are the 

 birds that are seen clustering and hovering on sunny 

 mornings and evenings round towers and steeples, and on 

 the roofs of churches and houses. These congregatings 

 usually begin to take place about the first week in August ; 

 and therefore we may conclude that by that time the first 

 flight is pretty well over. The young of this species do 

 not quit their abodes altogether; but the more forward 

 birds get abroad some days before the rest. These approach- 

 ing the eaves of buildings, and playing about before them, 

 make people think that several old ones attend one 

 nest. They are often capricious in fixing on a nesting-place, 

 beginning many edifices, and leaving them unfinished ; but 

 when once a nest is completed in a sheltered place, it serves 

 for several seasons. Those which breed in a ready finished 

 house get the start in hatching of those that build new by 

 ten days or a fortnight. These industrious artificers are at 

 their labours in the long days before four in the morning. 

 When they fix their materials they plaster them on with 

 their chinsy moving their heads with a quick vibratory 

 motion. They dip and wash as they fly sometimes in very 

 hot weather ; but not so frequently as swallows. It has 

 been observed that martins usually build to a north-east or 

 north-west aspect, that the heat of the sun rpay not crack 



