BIRDS IN GENERAL 419 



but are secreted amidst the clefts and caverns of those 

 abrupt cliffs where they usually spend their summers. 



The late severe weather considered, it is not very 

 probable that these birds should have migrated so early 

 from a tropical region, through all these cutting winds and 

 pinching frosts : but it is easy to suppose that they may, 

 like bats and flies, have been awakened by the influence of 

 the sun, amidst their secret latebrae, where they have 

 spent the uncomfortable foodless months in a torpid state, 

 and the profoundest of slumbers. 



There is a large pond at Wish-hanger, which induces 

 these sand-martins to frequent that district. For I have 

 ever remarked that they haunt near great waters, either 

 rivers or lakes. 



SWALLOWS, CONGREGATING AND 

 DISAPPEARANCE OF 



During the severe winds that often prevail late in the 

 spring, it is not easy to say how the hirundines subsist : 

 for they withdraw themselves, and are hardly ever seen, 

 nor do any insects appear for their support. That they 

 can retire to rest, and sleep away these uncomfortable 

 periods, as bats do, is a matter rather to be suspected than 

 proved : or do they not rather spend their time in deep 

 and sheltered vales near waters, where insects are more 

 likely to be found ? Certain it is, that hardly any indi- 

 viduals of this genus have at such times been seen for 

 several days together. 



September 13, 1791. The congregating flocks of 

 hirundines on the church and tower are very beautiful 

 and amusing ! When they fly off together from the roof, 

 on any alarm, they quite swarm the air. But they soon 

 settle in heaps, and preening their feathers, and lifting up 

 their wings to admit the sun, seem highly to enjoy the 

 warm situation. Thus they spend the heat of the day, 

 preparing for their emigration, and, as it were, consulting 

 when and where they are to go. The flight about the 



