MISTLETOE-THRUSH. 263 



rounder ; wings and tail beneath grey : tarsi and toes pale 

 brown ; claws dark brown. Males and females differ little 

 in size or plumage. 



The whole length is about eleven inches : the wing from 

 the carpal joint, five inches and three-quarters ; the first 

 primary one inch ; the second the same length as the fifth ; 

 the third and fourth equal, and the longest. 



The young, when about to leave the nest, exhibits a greater 

 variety of markings than the adult ; the feathers on the head, 

 neck, upper part of the back, and smaller wing-coverts, have 

 a median stripe of buff, with a black spot at the tip ; those 

 of the greater coverts and tertials have broad external edges 

 of rich buff : the chin is white ; the other lower parts tinged 

 with fawn-colour and marked with black spots. 



As in all the truly British Thrushes, pale or white varieties 

 of this species have been met with ; and, indeed examples 

 exhibiting partial or total albinism are so far from rare 

 among birds generally, that it is proposed not to mention 

 them in the course of this work unless in such cases as 

 possess some special interest. Though much has been written 

 on the subject, little appears to be known as to the cause 

 of these variations. It has been supposed, and probably with 

 truth, that they are usually due at first to constitutional 

 weakness, which experience shews to be often hereditary ; 

 but it must be remarked that the tendency to albinism is 

 much more frequent in some groups than in others. 



The vignette represents the breast-bone of the Blackbird 

 illustrating its form in the genus Turdus. 



