276 INSTINCTS OF BIRDS. 



that a pair of ravens nesting in tlie rock of 

 Gibraltar would suffer no vulture or eagle to rest 

 near their station, but would drive them from 

 the hill with amazing fury ; and that even the 

 blue thrush, at the season of breeding, would 

 dart out from the clefts of the rocks to chase 

 away the kestril or the sparrow-hawk. Indeed, 

 so regardless of danger are some species while 

 their nestlings are small, that I have known the 

 redbreast, whinchat, great titmouse, &c., when 

 introduced to their nests, after having been 

 forcibly removed to a distance from their un- 

 fledged young, remain quietly upon them as if 

 they had not been molested. Yet, although this 

 instinct, the transient effects of which depend 

 most likely on a temporary excitation of the 

 parental feelings by some physical modification 

 of the corporeal organs, thus for a time power- 

 fully predominates, its manifestations are never- 

 theless frequently influenced by the active co- 

 operation of the intellectual faculties, as in the 

 following examples. 



*'The flycatcher,*' says Mr. White,* "builds 

 every year in the vines that grow on the walls 

 of my house. A pair of these little birds had 

 one year inadvertently placed their nest on a 



* Natural History of Sclbornc, p. 151. 



