ON THE SLEEP OF BIRDS. 57 



mode of resting and sleep : for the Duck and Goose, although 

 they do not perch, will frequently sleep standing on one leg 

 upon the ground, with their heads turned round, and the bills 

 under the wings. The common Cock and Hen, although 

 they invariably perch, if a perch can be obtained, do not, 

 when sleeping, rest usually on one leg, but they sink down 

 with their bodies upon the perch, having their legs com- 

 pressed under them. The common Field Lark sleeps upon 

 the ground with his legs also similiarly compressed. It is 

 probable also, that all the tribe of birds, even thePerchers, 

 occasionally sink down with their bodies resting on the 

 perch during their soundest sleep. And, what is very re- 

 markable in the structure of their feet and legs, the greater 

 the weight upon the muscles, the more firmly the claws 

 grasp whatever they lay hold of; hence the cause that 

 birds do not fall down in sleep although most of their senses 

 are dormant. 



The motion of the branches of trees produced by the 

 wind increases, doubtless, the disposition for sleep in many 

 birds; this may be exemplified in the Common Fowl: for 

 placing its bill under the wing, even in broad daylight, 

 and swaying it to and fro in the hand for a very short time, 

 will produce sleep: a beautiful proof of the adaptation of 

 birds to the function. 



Most of the tribe of birds sleep during the night ; but 

 there are many exceptions to this. Owls in particular are, 

 during the night, much more active than in the day ; their 

 sight, similar to that of cats, appears to serve them best in 

 the dark. Many of the Duck tribe are not only wakeful, 

 but feed during the night ; so also do the Goatsuckers. 

 The Nightingale, and a few other song birds, are also 

 wakeful while in song, during, at least, some portion of the 

 night ; and even the Cuckoo will be occasionally found a 



