The Philosophy of Birds' Nests. 417 



bristles. They cannot build a nest of twigs or fibres, hair or 

 moss, like other birds, and they therefore generally dispense 

 with one altogether, laying their eggs on the bare ground, or 

 on the stump or flat limb of a tree. The hooked bills, short 

 necks and feet, and heavy bodies of parrots, render them quite 

 incapable of building a nest like most other birds. They can- 

 not climb up a branch without using both bill and feet ; they 

 cannot even turn round on a perch without holding on with 

 their bill. How, then, could they inlay, or weave, or twist the 

 materials of a nest ? Consequently, they all lay in holes of 

 trees, the tops of rotten stumps, or in deserted ants' nests, the 

 soft materials of which they can easily hollow out. 



Now I believe that throughout the whole class of birds the 

 same general principles will be found to hold good, sometimes 

 distinctly, sometimes more obscurely apparent, according as 

 the habits of the species are more marked, or their structure 

 more peculiar. It is true that, among birds differing but little 

 in structure or habits, we see considerable diversity in the 

 mode of nesting, but we are now so well assured that important 

 changes of climate and of surface have occurred within the 

 period of existing species, that it is by no means difficult to 

 see how such differences have arisen. Habits are known to be 

 hereditary, and as the area now occupied by each species is 

 different from that of every other, we may be sure that such 

 changes would act differently upon each, and would often bring 

 together species which had acquired their peculiar habits in 

 distinct regions and under different conditions. 



But, it is objected, birds do not learn to make their nest as 

 man does to build, for all birds will make exactly the same 

 nest as the rest of their species, even if they have never seen 

 one, and it is instinct alone that can enable them -to do this. 

 No doubt this would be instinct if it were true, and I simply 

 ask for proof of the fact. This point, although so important 

 to the question at issue, is always assumed without proof, and 

 even against proof, for what facts there are, are opposed to it. 

 Birds brought up from the egg in cages do not make the 

 characteristic nest of their species, even though the proper 

 materials are supplied them, and the experiment has never 

 been fairly tried of turning out a pair of birds so bx'ought up 

 into an enclosure covered with netting, and watching the result 

 of their untaught attempts at nest-making. With regard to 

 the song of birds, however, which is thought to be equally 

 instinctive, the experiment has been tried, and it is found that 

 young birds never have the song peculiar to their species if 

 they have not heard it, whereas they acquire very easily the 

 song of almost any other bird with which they are brought up. 

 It is also especially worthy of remark that they must be taken 



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