282 Journal of Travel and Natural History 



the woods of our own island would detect the fallacy of classi- 

 fying nests as regards their eflficiency in point of concealment 

 according to their open or domed structure. Many of the 

 nests which are the best concealed are the slightest, the shallowest, 

 and the most open. Some of those, on the contrary, which 

 are most easily and most commonly found are those which are 

 necessarily bulky from the very perfection of their architec- 

 ture. Few nests are more easily found than those of the com- 

 mon Wren, and this in spite of the most wonderful construc- 

 tive skill in adapting the material of the nest to the vegetation 

 among which it may be placed. But the compactness of the 

 structure, its size, and its beautifully domed shape, very readily 

 betray it to the eye. On the other hand, the comparatively 

 shallow and loose nests of the Blackcap, Garden Warbler, and 

 Whitethroat, are most difficult to find, on account of their very 

 slightness, rendering them singularly inconspicuous among the 

 tangled growths in which they are skilfully concealed. 



So far, then, it does not appear that Mr Wallace's idea of the 

 functional perfection of nests, if consistently applied, would at all 

 justify the classification which he seeks to found upon it. On the 

 contrary, the function of concealment is secured very often with 

 the least degree of efficiency by the very kind of nest which he 

 represents as securing it most completely. 



We now come to the special theory for which Mr W^allace has 

 been preparing the way. " Turning from the nests to the 

 creatures who make them, let us consider," says Mr W^allace, 

 " birds themselves from a somewhat unusual point of view, and 

 form them into separate groups, according as both sexes, or the 

 males only, are adorned with conspicuous colours." There is, no 

 doubt, a very remarkable difference among birds in this respect. 

 Tliere is a large number of species among which the rule prevails, 

 that bright colours are confined to the male, the females having 

 plumage of dull or neutral tints. There is, on the other hand, 

 another large number of species among which this rule does not 

 prevail, and in which both sexes are equally brilliant in their 

 colouring. Now, two questions arise in respect to these facts. One 

 question is this, " Can any reason be assigned why dull colouring 

 should be given to the female birds of any species ?" The second 

 question is this, " Can any physical cause be discovered by which 

 this object, if it be an object, has been carried into effect ?" 



To the first of these questions, at least as regards many species. 



