0)1 Mr Wallace's Theory of Birds' Nests 281 



we have a classification of birds which professes to be founded on 

 their nests, but which, nevertheless, treats as matters of perfect in- 

 difference the structure, and the material, and the situation of 

 those nests — which brings into one group the long-tailed Tit, which 

 builds a receptical for its eggs and young of the most exquisite 

 beauty, and the Kingfisher, which vomits a few bones in the bottom 

 of a hole and lays its eggs upon them. In like manner it groups 

 together in the second class birds which build with every variety 

 and degree of skill, and birds which build no nest at all, but lay 

 their eggs upon the bare ground. Mr Wallace is so absorbed in 

 his preconceived idea that he faces this result without any apparent 

 consciousness that it makes a very near approach to a reductio ad 

 absurdum. " It \\all be seen," he says, " that this division of birds, 

 according to nidification, bears little relation to the character of 

 the nest itself It is a functional, not a structural, classification. 

 The most rude and the most perfect specimen of bird architecture 

 are to be found in both sections." 



But Mr Wallace does not see that even his idea of the "func- 

 tion" of birds' nests, as distinguished from their structure, material, 

 and situation, involves total forgetfulness of some of the most im- 

 portant circumstances which determine their fitness for the dis- 

 charge of that function. The one circumstance on which Mr 

 Wallace fixes his attention, regardless of all others, is the circum- 

 stance whether the eggs and young of sitting birds are or are not 

 what he calls " exposed to view." That is to say, he makes, or 

 professes to make, the one circumstance of concealment his prin- 

 ciple of classification. But this principle he applies only to the 

 contents of nests, and not to the nests themselves. He forgets 

 that the very form or structure of nests which most completely 

 covers up the eggs, or the sitting bird may, and often does, render ■ 

 the nest itself only more conspicuous. Thus a domed nest is a 

 larger structure, and one more easily observed than the smaller 

 nests, which are nevertheless open and uncovered at the top. 

 But, for the purpose of security and concealment, a nest is perfectly 

 useless which merely covers up the eggs, but attracts attention to 

 itself by its bulk, or its peculiarity of structure. It is the situation 

 of nests, and their closed or open character, on which their safety 

 from concealment depends. Predatory animals, from which danger 

 to nests arises, do not require to see the eggs if they can see the 

 nest. If they can find a nest, they know very well what they 

 will find inside of it. Any schoolboy who has ever nested in 



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