THE SLEEP OF BIRDS 155 



if the weather is very stormy the fathers may seek 

 trees with denser branches than the nest-trees, and 

 there all roost together. When the young rooks 

 are so big that they fill the nest the wives join the 

 husbands to roost in a place apart. 



There may be in a rookery some young birds who 

 have not succeeded in finding mates. These will 

 flock together to roost, and after the others have 

 turned in for the night may be heard quarrelling, or 

 perhaps revelling, and keeping, it is to be feared, dis- 

 gracefully late hours. 



Sparrows always make a great to-do before settling 

 down for the night ; they quarrel and bicker as a 

 matter of course and if one should come in to the 

 roosting-place very late, some hard things are sure 

 to be said to him for disturbing others. Sparrows 

 keep their wits about them when asleep, and some are 

 sure to make good their escape even when the 

 stealthiest of sparrow-catchers uprear the deadly net 

 against their roosting-place. 



Most birds, if disturbed while asleep, give an in- 

 dignant cry and take wing, but soon settle again, 

 possibly at once returning to their chosen resting-place. 

 Some sleep most heavily after feeding. Vultures that 

 have gorged on a carcase fall into a lethargic state, 

 to allow the food to be prepared and softened in the 

 crop for digestion ; and travellers tell how they will then 

 even permit themselves to be taken in hand, though 

 on becoming aware of danger they are alert enough. 

 As if knowing that the heavy meal has deprived them 

 of their wits, their first action often is to disgorge their 

 food! 



Some birds burst into song when disturbed from 

 sleep, like the sedge-warbler, who roosts in reeds on 

 the margin of water, or the merry-hearted little wren, 



