Mr Black wall on the Instincts of Birds. 259 



pronounce single words, and even short sentences, with tolerable 

 exactness. Yet, although 1 have excellent opportunities of ob- 

 serving the last species, and have been almost in the daily prac- 

 tice of investigating, I never knew it display any unusual ex- 

 ertion of its capacity for imitation in a state of nature, though, 

 when domesticated, it appears to have this faculty more highly 

 developed than almost any other British bird. 



The congregating of gregarious birds, which takes place in 

 the autumn, when they have finished breeding, is perhaps in- 

 tended to promote their mutual security, as they are much less 

 liable to be surprised by enemies, when associated together in 

 large numbers, than they are when separate. What tends to 

 strengthen this opinion is the fact, that some species provide for 

 the general safety, by appointing sentinels to give notice of ap- 

 proaching danger. This social disposition, which (with the well 

 known exception of rooks) usually continues no longer than the 

 next pairing season, seems, from the uniformity of the actions 

 that result from it, to be of instinctive origin ; though it cer- 

 tainly would be difficult to bring any direct proof that such is 

 the case. 



In treating of the migration of birds, Dr Darwin observes, 

 that as all species are capable of remaining throughout the year 

 in those countries in which they were bred, any departure from 

 them must be unnecessary, and therefore cannot be instinctive. 

 This reasoning, however, is extremely fallacious, inasmuch as it 

 restricts the operations of instinct solely to what is necessary ; 

 whereas we have seen that the singing of birds, and the practice 

 of concealing their superfluous food, though not absolutely indis- 

 pensable, are, nevertheless, decidedly instinctive. It is, moreover, 

 built on the gratuitous assumption, that several of the periodical 

 summer birds, as the swallow, flycatcher, cuckoo, goat-sucker, 

 &c., which feed almost entirely on insects, and consequently would 

 not be able to procure a sufficient supply of nourishment in the 

 winter months, have the property of passing the cold season in a 

 state of torpidity ; an hypothesis directly at variance with well- 

 established facts. Indeed, how very defective and unsatisfactory 

 the arguments advanced in support of the hybernating system 

 are, does not require insisting upon, as those who have consi- 

 dered the subject impartially, must be well aware, that they are 



r2 



