INTRODUCTION. 25 



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 mo- 

 tions are often principally nocturnal, except in the cold and desolate 

 northern regions, where they usually retire to breed. Other birds are 

 so powerfully impelled by this governing motive to migration, that 

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

 Plovers, Swans, Cranes, Wild Geese, Storks, &c. When untoward 

 circumstances render haste necessary, certain kinds of birds, which 

 ordinarily travel only in the night, continue their route durino- the 

 day, and scarcely allow themselves time to eat : yet the singing 

 birds, properly so called, never migrate by day, whatever may hap- 

 pen 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 povrerful 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 seekincr 

 repose, as usual, they manifest great agitation, sing without ceasino- 

 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 facilitatino- 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 or graze the surface of the deep. If 

 the Wren, the Creeper, and the Titmouse rest for an instant on a 

 tree to snatch a hasty morsel, in the next they are on the wino- to 

 fulfil their destination. However abundant may be the nourishment 

 which presents itself to supply their Avants, in general, birds of pas- 

 sage rarely remain more than two days together in a place. 



The cries of many birds, while engaged in their aerial vovawe are 

 such as are only heard on this important occasion, and appear ne- 

 cessary for the direction of those which fly in assembled ranks. 



During these migrations, it has been observed, that birds fly ordi- 

 narily in the higher regions of the air, e^xcept when fogs force them 

 to seek a lower elevation. This habit is particularly prevalent with 

 Wild Geese, Storks, Cranes, and Herons, which often pass at such a 

 height as to be scarcely distinguishable. 



3 



