Williams, Color in Relation to Inheritance. 



321 



The Black-backed Goose of India and Africa (Sarcidiornis 

 melanonota) also shows a similar black and white plumage, and 

 a fleshy knob on the beak, but ' variation ' is driving the black 

 from the head and neck, which presents, in consequence, a 

 most curiously speckled appearance. 



In the Wood Duck (Aix sponsa) which also belongs to this 

 group, variation has certainly got the upper hand : the fleshy knob 

 has been succeeded by a crest of beautiful feathers; and, 

 altogether, the bird has become one of the handsomest of its 

 tribe ; though it still retains the dark glossy back and wings, and 

 the long rounded tail feathers, which are distinguishing marks of 

 nearly all the subfamily. 



The Pigeons and Ducks afford an illustration of the inheritance 

 of general colors ; but, in some groups, patches and spots of 

 special color seem to be inherited, and become recognition 

 marks of several allied families. 



The strong tendency of the Woodpeckers to display a patch 

 of red, or sometimes yellow, on the head of the male bird is well 

 known ; but the three other, most nearly allied, families of the 

 zygodactyle Picaris, viz., the Barbets, Toucans, and Honey- 

 guides, have a similar tendency to show a red or yellow patch on 

 the head or the rump, sometimes on both. 



More than ninety of the hundred and twelve known species of 

 Barbet display patches of one or other of these colors, and the 

 few that are without them are generally dull colored birds. 



In the Toucans the crimson or scarlet patch on the rump or 

 crissum is a marked feature of the family. In a few species the 

 patch is chestnut ; but there are only four or five of the fifty-nine 

 recognized species that are altogether without it. 



Nine out of the twelve Honey-guides have some shade of yellow 

 on the lower back or rump, and two, out of the three exceptions, 

 have a white patch. 



Like the Woodpeckers, these three families all nest in hollow 

 trees, and lay white eggs. 



Their national colors are, evidently, red and yellow. 



The Kingfishers are as remarkable for their attachment to 

 blue, or sometimes green, as the Woodpeckers to red. Many 

 species are almost entirely blue on the upper surface, in others 



