318 BIRD BEHAVIOUR 



in trees. Its short front and rudimentary hind 

 toes are most ill-adapted for such a habit, and 

 Waterton considered it maintained its position by 

 the rough scales at the back of the shank. 



Some birds roost by hanging themselves up, 

 either suspended absolutely head- downwards like 

 bats, which is done only by the little Bat-Parrots 

 (Loriculus), or by clinging to some support head- 

 upwards, but suspended against it by the claws, 

 like Woodpeckers, Colies or Mouse-birds, and some 

 at any rate of the Swifts. Swifts of the most 

 typical kinds, however, like ours and the Indian 

 and African House-Swift (Cypselus affinis), roost in 

 their nests, a habit rare among birds, but also 

 followed by Martins, Tits, Owls, Petrels, and the 

 common Pigeon and Wren. In the case of the 

 latter, many birds will crowd into one nest or hole 

 in winter, and even then often die in a hard frost. 



