SEXUAL SELECTIONNESTING OF BIRDS. 229 



well concealed that little absolute risk is incurred. 

 Here I might record an exceptional instance of 

 mimicry practised by this species, and which only 

 came under my notice a few days ago (April 1893). 

 I found a Blackbird's nest wedged deeply amongst 

 ivy growing thickly over a stump in a hedgerow. 

 To conceal the rim of the nest the old bird had 

 placed several large tufts of green moss round it, 

 making it blend so beautifully with the green ivy 

 leaves that nothing but the keenest scrutiny could 

 detect the fraud ! This is a wonderful instance 

 of deviation from architectural type, and shows how 

 readily a change in the entire nest-building habits 

 of a species could be initiated. 



I am quite prepared to admit that my researches 

 into the little known subject of bird architecture and 

 the colours of eggs are to a large extent hypothetical 

 and not open to absolute proof; but in the entire 

 absence of any better or more feasible explanations 

 of the various complex phenomena, I venture to 

 think that those already offered are at least scientific 

 and logical, and in accordance with the advanced 

 views of the present day. Certainly Mr. Allen 

 appears not to have anything to suggest in place of 

 the theories advanced by Dr. Wallace and myself. 

 I have already shown in my essay and elsewhere 



