ORGANS OF VOICE. 63 



its affection and interests are awakened by attention to its 

 mate, during the time of rearing its young. The male may 

 then be generally seen on some twig or bough, at no great 

 distance from the nest ; in most cases becoming silent if 

 aware of a stranger's approach, or exchanging the note 

 of pleasure for another of anger and complaint, which too 

 often produces the very evil it dreads. Thus, the Nightin- 

 gale, one of our shyest and most timid birds, will frequently 

 discover its nest, by making a jarring noise, and also a 

 snapping and cracking, at the same time pursuing people 

 along the hedges, as they walk, when its young are in a helpless 

 state. The male Blackcap is still more incautious, for it will 

 commence and continue its song, even when sitting on its 

 nest, and thus too frequently become the innocent cause of 

 the capture of its brood. 



The loud cries of other birds, however, particularly of 

 many of the migratory water-birds, which fly by night, are 

 evidently intended for the purpose of keeping them together. 

 Few have been without opportunities of listening in the 

 silence of the night to the incessant cackling of a flight of 

 wild Geese, on their way to some distant spot, high in the 

 air. In the Northern seas, sounds of this sort are more fre- 

 quently heard, from birds which never come so far to the 

 southward. . Of these is the red-breasted Diver, which seldom 

 quits the water by day, but during the night may be known 

 to be on the wing, at a vast height, by a peculiarly melan- 

 choly and distressing scream, exactly resembling that of 

 a young child suffering from agonizing pain. We have 

 listened by the hour together to the repeated and successive 

 wailings of these wild, melancholy birds ; first, the scream is 

 faint, and so distant as scarcely to reach the ear; then it 

 increases as the bird passes nearer, till, as it continues its 

 flight, the sound gradually dies away. Soon another scream 

 from another quarter is faintly heard ; and so on, till the dawn 

 appears, when they betake themselves to the element on 

 which they pass the day. 



The distance, too, at which some birds may be heard is 

 very extraordinary. The brown Crane of North America, 



