138 Mr. George J. Bomanes [Feb. 8, 



and in America this change has taken place within the last two or 

 three hundred years. Indeed, according to Captain Elliott Cones, all 

 the species of swallow on that continent (with one possible exception) 

 have thus modified the sites and structures of their nests in accord- 

 ance with the novel facilities afibrded by the settlement of the 

 country. 



Another instructive case of an intelligent change of instinct in 

 connection with nest-building is given from a letter by Mr. Haust, 

 dated New Zealand, 1862, which I find among Mr. Darwin's manu- 

 scripts. Mr. Haust says that the Paradise duck, which naturally or 

 usually builds its nest along the rivers on the ground, has been 

 observed by him on the east of the island , when disturbed in their 

 nests upon the ground, to build " new ones on the tops of high trees, 

 afterwards bringing their young ones down on their backs to the 

 water ; " and exactly the same thing has been recorded by another 

 observer of the wild ducks of Guiana. Now if intelligent adjustment 

 to peculiar circumstances is thus adequate, not only to make a whole 

 breed or species of bird transport their young upon their backs — or, 

 as in the case of the woodcock, between their legs — but even to make 

 web-footed water-fowl build their nests in high trees, I think we can 

 have no doubt that if the need of such adjustment were of sufficiently 

 long continuance, the intelligence which leads to it would eventually 

 produce a new and remarkable modification of their ancestral instinct 

 of nest-building. 



Turning now from the instinct of nidification to that of incuba- 

 tion, I may give one example to show the plasticity of the instinct in 

 relation to the observed requirements of progeny. Several years ago 

 I placed in the nest of a sitting Brahma hen, four newly-born ferrets. 

 She took to them almost immediately, and remained with them for 

 rather more than a fortnight, when I made a separation. During the 

 whole of the time the hen had to sit upon the nest, for the young 

 ferrets were not able to follow her about, as young chickens would 

 have done. The hen was very much puzzled by the lethargy of her 

 offspring, and two or three times a day she used to fly off the nest 

 calling on her brood to follow ; but, on hearing their cries of distress 

 from cold, she always returned immediately, and sat with patience 

 for six or seven hours more. I found that it only took the hen one 

 day to learn the meaning of these cries of distress ; for after the first 

 day she would always run in an agitated manner to any place where 

 I concealed the ferrets, provided that this place was not too far 

 away from the nest to prevent her from hearing their cries. Yet 

 I do not think it would be possible to imagine a greater contrast 

 between two cries than the shrill piping note of a young chicken, and 

 the hoarse growling noise of a youug ferret. At times the hen used 

 to fly off the nest with a loud scream, which was doubtless due to the 

 unaccustomed sensation of being nipped by the young ferrets in their 

 search for the traditional source of mammalian nutriment. It is 

 further worthy of remark that the hen showed so much anxiety when 



