522 THE PIGEONS 



But even here it is now difficult to secure pure-bred birds, owing to inter- 

 breeding with dove-cot pigeons decoyed away from home. Last year 

 (1910) I endeavoured to secure pure-bred birds from caves in Donegal, 

 but out of about twenty birds shot all but two showed more or less 

 evident traces of interbreeding with house-pigeons : some could not be 

 distinguished from " blue-rocks." Darwin, it may be remembered, long 

 ago drew attention to a very curious fact in regard to the coloration 

 of the rock-dove, and the domesticated variety thereof, which so far 

 has received no explanation. " There seems," he says, " to be some 

 relation between the croup being blue or white, and the temperature 

 of the country inhabited by both wild and dove-cot pigeons ; for 

 nearly all the dove-cot pigeons in the northern parts of Europe have 

 a white croup like that of the wild European rock-pigeon ; and nearly 

 all the dove-cot pigeons of India have a blue croup like that of the 

 wild C. intermedia of India." 



Are we to infer from this that the presence or absence of pigmenta- 

 tion is determined by climate ? or that the white area is a colour 

 variation, or colour "mutation," whose presence or absence is deter- 

 mined by Mendelian factors ? That is to say, the coloration of the 

 rump is determined not by climate, but by germinal variation, and the 

 interbreeding of birds presenting two forms of this variation. There 

 are inexplicable and contradictory features in either interpretation, 

 and it were profitless to pursue the theme further. Let it suffice to 

 draw attention to the problem, which stands where it was when 

 Darwin propounded it 



THE TURTLE-DOVE 

 [W. P. PYCRAFT] 



The turtle-dove differs conspicuously from our other native 

 pigeons in coloration, the dominant hue of the upper parts being 

 ochreous yellow, while the beautiful metallic iridescence of the neck 

 is entirely wanting. Furthermore, unlike its congeners in these 



