SYLVIA SCTORIA. 



we see in the winter season bands of wolves, impelled by hunger, 

 descend from the hills or forests and ravage the stock of the 

 farmer, an enterprise on which they never venture when other 

 food can be obtained at less risk. In such cases, however, when 

 the immediate object of their enterprise has been accomplished, 

 their antisocial instinct revives, and they disperse, often quarrelling 

 among themselves. , 



79. Various species which do not habitually live in society, 

 nevertheless assemble in vast numbers, when at certain seasons 

 they make long journeys. This is the case generally with migra- 

 tory animals. The social instinct is, however, only temporary, 

 since, when the journey is completed, and they arrive at their 

 destination, they disperse. 



80. The migratory pigeons of North America present a remark- 

 able example of this instinct, of temporary and periodical soci- 

 ability. These birds, when stationary, are dispersed in vast 

 numbers over the country, but when about to migrate, they 

 assemble in inconceivable numbers, and perform their journey 

 together, flying in a close and dense column nearly a mile in 

 width, and six or eight miles in length. "Wilson, the well-known 

 American ornithologist, saw a flock of these birds pass over him in 

 the state of Indiana, the number of which he estimated at two 

 millions. The celebrated Audubon related that one day in autumn, 

 having left his house at Henderson, on the banks of the Ohio, he 

 was crossing an inclosed tract near Horsdensburgh, when he saw 

 a flight of these pigeons, more than commonly numerous, directing 

 their course from the north-west towards the south-east. As he 

 approached Louisville, the flock became more and more numerous ; 

 he described its density and extent to be such, that the light of 

 the sun at noon was intercepted, as it would have been by an 

 eclipse, and that the dung fell in a thick shower like flakes of 

 snow. Upon his arrival at Louisville, at sunset, having travelled 

 fifty-five miles, the pigeons were still passing in dense files. In 

 fine, this prodigious column continued to pass for three entire days, 

 the whole population having risen and resorted to fire-arms to 

 destroy them. 



The usual habitations of these birds are the extensive woods 

 which overspread that vast continent. A single flock will often 

 occupy one entire forest ; and when they remain there some time, 

 their dung is deposited on the ground in a stratum several inches 

 thick. The trees are stript throughout an extent of many thou- 

 sand acres, and sometimes completely killed, so that the traces of 

 their visit are not effaced for many years. 



81. Of all mammifers, the Canadian beaver is the most remark- 

 able for sociability, industry, and foresight. During the summer 



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