THE TURTLE-DOVE PATTERN IN OTHER ORDERS OF BIRDS. 121 



Mr. Keeler's 17 observations on sex dimorphism and seasonal color changes of 

 American woodpeckers deserve mention and a word of comment: 



The female (at the breeding-season) advances towards the male color, as is shown in 

 the woodpecker, Sphyrapicus varius. We have three species S. varius of the East, S. 

 nuchalis of the Rocky Mountain district, and S. ruber of the Pacific coast. The red color 

 increases from east to west, being least in S. varius, more in S. nuchalis, and most in 

 S. ruber. 



Keeler concludes that the variation is a climatic modification. This is an un- 

 warranted assumption. Had the red diminished, the assumption would have been 

 the same; or, if any change whatever of a gradual kind could be found it would be 

 credited to climatic influence. 



The young of Sphyrapicus varius and S. nuchalis are "mottled brown, and with 

 the colored areas of the adult male white." The adult female of 8 varius in winter 

 still has the white areas, but has black and gray in place of the brown of the young, 

 and only a few dots of red on the forehead. The adult female has the black strength- 

 ened in her breeding plumage, and the whole crown of the head is then red. The 

 adult male of S. varius has the same red crown and a red throat instead of white. 

 In the adult female of S. nuchalis we have a red crown and a little red on the throat, 

 while the adult male has more red than the male of S. varius. In the adult male of 

 S. ruber nearly the whole head, throat, and front neck are red. 



That the female Sphyrapicus varius should advance towards the male only 

 "during the breeding season," but still halt behind the male, in that she gets the 

 red crown but not a red throat, suggests that: 



(1) The red is not a male attribute, but merely a higher, development, which 

 the female accomplishes only imperfectly at the time of her highest energy, in winter 

 sinking back still lower, or nearer the Juvenal condition. 



(2) Both sexes have the same germ foundation, the distinctions of the male 

 being, as it were, the distinctions of the female carried higher. 



(3) In this one species (the lowest of the three) we have four stages : (a) Juvenal 

 brown and white areas; (6) female winter plumage black and white areas; (c) 

 female summer plumage red, black, and white areas; and (d) adult male plumage- 

 black, white, and two red areas. The red throat is a male distinction in this 

 species, but in another species (Sphyrapicus nuchalis) the female rises to the same 

 distinction, but in weaker development, and the male also goes a little higher than 

 in S. varius, enlarging somewhat both the red crown and the red throat. Finally. 

 in S. ruber the two red surfaces are further increased in the male until they fuse on 

 the sides of the head. Thus we have in the three species at least seven stages, in 

 six of which red is present in as many different degrees. 



THE TURTLE-DOVE PATTERN AND ITS MODIFICATION IN VARIOUS FORMS. 



Paying special heed to the color-patterns of immature birds, and to sequence 

 of patterns presented in the young and the adults of both sexes, I soon found con- 

 vincing evidence, in great abundance, that the pigeon unit of pattern was at the 

 same time the avian unit. 



Pattern in the Juvenal robin In view of Hacker's investigations on the evolu- 

 tion of pattern in birds, and especially the thrushes and their allies, the markings 



17 L. c., pages 244, 245, pi. xv. 



