Hybrid Birds 



argued that species which have got no further in 

 separation than a different plumage are not as yet 

 fully distinct, but rather comparable to the colour- 

 varieties in our domesticated birds. That the 

 intermediate birds represent the ancestors of the 

 two forms does not seem at all probable, because 

 the evidence is in favour of colour-varieties 

 appearing suddenly, and not by gradations 

 from an intermediate type. Thus, there are 

 two forms of the common peacock, the typical 

 (Pavo cristatus) and the black-winged (Pavo 

 nigripennis), but there has never been an inter- 

 mediate ancestor to these, for we know for a fact 

 that the black-winged form, like the albino one, 

 arises quite suddenly from the ordinary bird. It 

 may also be remarked that the free interbreeding 

 of forms or species separated only by colour is a 

 fatal blow to the common theory that colour- 

 differences are "recognition-marks" by which 

 birds of a feather are enabled to flock together. 



The fertility of undoubted hybrids — between 

 species where other points combine with colour 

 to make a distinction admitted by every one — is 

 still very widely disbelieved. And there is some 

 reason for the disbelief, since it appears to be the 

 case that the commonest bird-hybrids, the "mules" 

 between various British finches and the canary, 

 are usually barren, though they will pair, lay, and 

 sit in the most exemplary way, a hen " mule " 



'5 



