INTRODUCTION. XXxix 



after rearing their young. Some are so given to wandering 

 that their choice of a country is only regulated by the resources 

 which it offers for subsistence ; such are the Pigeons, Herons 

 of several kinds, Snipes, wild Geese and Ducks, the wandering 

 Albatros, and Waxen Chatterer. 



The greater number of birds travel in the night ; some 

 species, however, proceed only by day, as the diurnal birds of 

 prey, — Crows, Pies, Wrens, Creepers, Cross-bills, Larks, Blue- 

 birds, Swallows, and some others. Those which travel wholly 

 in the night are the Owls, Butcher Birds, Kingfishers, Thrushes, 

 Flycatchers, Night Hawks, Whip-poor-wills, and also a great 

 number of aquatic birds, whose motions are also principally 

 nocturnal, except in the cold and desolate northern regions, 

 where they usually retire to breed. Other birds are so pow- 

 erfully impelled by this governing motive to migration that 

 they stop neither day nor night ; such are the Herons, Mota- 

 cillas. Plovers, Swans, Cranes, Wild Geese, Storks, etc. When 

 untoward circumstances render haste necessary, certain kinds 

 of birds, which ordinarily travel only in the night, continue 

 their route during the day, and scarcely allow themselves time 

 to eat ; yet the singing-birds, properly so called, never migrate 

 by day, whatever may happen to them. And it may here be 

 inquired, with astonishment, how these feeble but enthusiastic 

 animals are able to pass the time, thus engaged, without the 

 aid of recruiting sleep ? But so powerful is this necessity for 

 travel that its incentive breaks out equally in those which are 

 detained in captivity, — so much so that although during the 

 day they are no more alert than usual, and only occupied 

 in taking nourishment, at the approach of night, far from seek- 

 ing repose, as usual, they manifest great agitation, sing without 

 ceasing in the cage, whether the apartment is lighted or not ; 

 and when the moon shines, they appear still more restless, as it 

 is their custom, at liberty, to seek the advantage of its light 

 for facilitating their route. Some birds, while engaged in their 

 journey, still find means to live without halting, — the Swallow, 

 while traversing the sea, pursues its insect prey; those who 

 can subsist on fish without any serious effort, feed as they pass 



