CHAPTER IV. 



THE ORIGIN AND RELATIONSHIPS OF THE ROCK-PIGEONS AS REVEALED IN 



THEIR COLOR-PATTERN. 1 



The wild rock-pigeons, universally regarded as the ancestral stock of all our 

 domestic pigeons, exhibit two very distinct color-patterns, one consisting of black 

 chequers uniformly distributed to the feathers of the wing and the back, the other 

 consisting of two black wing-bars on a slate-gray ground. The latter was regarded 

 by Darwin as the typical wing-pattern for Columba livia; the former was supposed 

 to be a variation arising therefrom, of frequent occurrence but of no importance. 



Just the contrary is true; the chequered pigeon represents the more ancient type, 

 from which the two-barred type has been derived. From this standpoint the 

 chequered type deserves the distinction of the specific name, Columba affinis, once 

 accorded to it but subsequently abandoned by Mr. Blyth. Columba livia could 

 well be reserved for the derived type. 



The direction of evolution in pattern in the rock-pigeons has been from a con- 

 dition of relative uniformity to one of regional differentiation. That seems reason- 

 able enough, and yet Darwin's view to the contrary rested on plausible grounds. 

 Indeed, the chequered wing might, at first sight, appear to be a departure from the 

 more to the less uniform condition; and this would be true with respect to the gray 

 surface, considered as a plain unadorned area, that originally included the entire 

 wing. The appearance of two bars would be the first break in uniformity, and the 

 extension of chequers, like those composing the bars, to all the coverts, might 

 seem like turning uniformity into variformity. On the other hand, if we attend to 

 the black chequers rather than to the gray ground, it is at once apparent that the 

 chequered wing presents a condition of fairly uniform distribution of like spots, 

 while the two-barred wing represents a long departure in the direction of regional 

 differentiation. 



It is quite natural to suppose that an unspotted stage preceded the spotted 

 one, but general theory of this kind is often misleading. Uniformity in color is 

 not always proof of simplicity. Some of the more highly developed colors, as 

 green and blue, may be quite as uniform as the gray of the pigeon's wing. Even 

 iridescence may sometimes extend more or less evenly to large surfaces and at times 

 characterize the plumage as a whole. The gray of the pigeon is certainly not to 

 be regarded as a primitive ancestral color. Its evolution has not been worked out, 

 but it is known that it is not a pure pigmental color. It is an effect produced by 

 the withdrawal of brown pigment from the superficial parts of the feather, and by 

 a segmental arrangement of the pigment granules in the barbules (Hacker). 



Gray in the pigeon is undoubtedly a relatively late acquisition, brown repre- 

 senting the simpler and more primitive color. Evidence of this is seen in the 



1 An address read November 18, 1903, to the National Academy of Sciences at the University of Chicago. The 

 slight amount of repetition of statements made in Chapter II will probably not prove a disadvantage to the reader. 

 Two pages of a manuscript (Z 10), written in 1907, have been added to amplify the briefer statements of the earlier 

 address. A detailed comparison of the individual spots or chequers in Columba livia and Columba affinis has been 

 included. The address of 1903 was also delivered at Woods Hole, and a one-page abstract of it published in the Bio- 

 logical Bulletin, Volume VI (1904), p. 307. That abstract is used as a partial summary of this chapter. — Ed. 



49 



