LINNEAN GENUS FALCO* 



615 



the other varieties, and is distinguished by the F-nig«-, 

 mature plumage of the head : " In utroque capitis 



cies, observes, " Pedes sunt plumheO'viridescentes ; prope di- 

 gitos magis ad flavum iiiclinant," {Syn, Meth, p. 95.) Edwarps 

 describes it with the legs of a " greenish-lead colour" inclimng to 

 yellow ; and, according to Buffon, it is described and figured 

 by Frisch with the legs of a yellow colour, as in the generality 

 of falcons. 



The preceding quotations, it will be observed, are conclusive 

 in regard to the variation in the external characters of the F, 

 niger ; and the descriptions by Brisson and Edwards, when 

 taken in conjunction with the other two, demonstrate the pro- 

 bability of a change sometimes taking place in the same indivi- 

 dual, as the birds described by Edwards, and in the Synopsis 

 Methodica, appear to have been intermediate between BuffoN's 

 and Frisch's, or, as it were, losing the blue tinge, and ac* 

 quiring the yellow one. This circumstance is interesting, both 

 in a general view, as connected with the physiology of birds, 

 and as illustrative of those variations, a knowledge of which i« 

 necessary to enable us to ascertain with tolerable certainty th» 

 distinctions between individuals exhibiting accustomed or acci- 

 dental changes, and such as i»ay be considered as peculiar and 

 permanent varieties, and in assisting us to determine the species 

 to which particular varieties ought to be referred. 



The colour of the legs in the F. niger, therefore, cannot be 

 considered as forming in any degree a specific distinction be- 

 tween it and the Peregrine Falcon. There is probably in diffe- 

 rent individuals, either a transition in colour from blue to yel^ 

 low, as I suppose to have been exemplified in the four birds de- 

 scribed by Buffon, Brisson, Edwards, and Frisch, or the 

 distinction is permanent, and may be considered to result from 

 that peculiarity in the constitution of the bird, which produces 

 the variation in the shade and markings of the plumage. 



