ON THE NATURAL HISTORY OF THE NIGHTINGALE. 213 



vessels ; by day they rest from their fatigue, and seek their food : 

 and, in perfect conformity with this, the Nightingale, and the vari- 

 ous migratory warblers, in confinement, very rarely evince any 

 peculiar restlessness by day ; but at night, more especially when a 

 light is brought into the room where they are kept, they are like 

 mad creatures, rapidly fluttering and flapping their wings, as if 

 flying with their heads continually pointing upward, and every 

 instant appearing as if about to spring into the air, which they 

 now and then do with such violence that Nightingales (for in- 

 stance) have been often known thus to fracture their skull against 

 the wooden roof-work of their cage. Of course, food can have 

 nothing to do with this, as birds in captivity have always a regular 

 supply ; their desire to migrate would seem to be wholly influenced 

 by the temperature, every change to colder weather in the autumn, 

 and generally during the winter, invariably occasioning this uneasi- 

 ness, while the same is always induced by a change to warmer 

 weather during the spring. When the temperature is more settled, 

 they are more quiet ; and although confined in a close and warm 

 room, it is surprising how quickly they feel every change that takes 

 place out of doors, which is sure to be indicated by their greater or 

 less desire to migrate. 



Various phenomena exhibited by migrant birds. — It is also worthy 

 of remark that, in confinement, most of the species particularly ex- 

 hibit this impulse in spring, in the exact order in which the wild 

 birds arrive in the country ; and that, in general, each kind be- 

 comes, in its turn, the most restless, precisely about a week or ten 

 days before that particular species makes its first appearance in its 

 proper haunts. In the wild birds, the migrative impulse seems always 

 to be wholly dissipated by their long journey ; for these, if captured 

 upon their arrival, never evince it ; whereas those which have lived 

 in captivity through the winter continue to shew it, at intervals, 

 during the greater portion of summer ; — that is to say, till they 

 have discontinued singing, and are about to undergo their autumnal 

 moult, from which time they do not again evince it till the proper 

 season arrives for leaving the country. Migratory birds captured 

 late in autumn exhibit it very strongly. 



Which cannot be accounted for on any secondary principles. — The 

 above numerous facts, which are deduced from the results of careful 

 observations made through several consecutive years, would appear, 

 in some instances, to be contradictory ; the birds are affected by 

 changes of temperature, and yet exhibit the migratory impulse in 

 summer, when the required degree of temperature is arrived at ; 



