1874.] 



315 [Ridgway. 



Paet II. Consideration of Climatic Influence upon Color, as mani- 

 fested in the Birds of the Lower Wabash Valley. 



The law of increased intensity of color to the southward is al- 

 ready well understood; 1 and that the birds of the Mississippi Valley 

 are more brightly colored than individuals of the same species from 

 parallel latitudes on the Atlantic coast is another law which Mr. 

 Allen's observations in Eastern Kansas have developed and which my 

 own in Southeastern Illinois confirm. On pages 113 and 115 of Mr. 

 Allen's paper, cited at the beginning of this article, that gentleman 

 tells us that " in the woodlands of Eastern Kansas a decided general 

 tendency to a greater intensity of color than at the northward was 

 noticed, in accordance with the law of the increase in intensity of 

 color to the southward, which in several* species was especially 

 marked. The males of the common indigo bird (Cyanospiza cyaned) 

 were not only much more than ordinarily lustrous, but the females 

 shared the blue tint of the males to an unusual degree." The cardinal 

 found there " makes a decided approach to the thick-billed race of 

 this bird found in Lower California (C. igneus auct.)." 



In regard to this law there is a striking analogy, with minor dis- 

 tinctive features to be noted afterwards, between Eastern Kansas 

 and Southeastern Illinois. Specimens of Cardinalis virginianus from 

 Mt. Carmel and Olney are as intensely red as those from Florida 

 while this tint is at the same time much purer; they have also about 

 the same general size and form, while the dimensions of the bill 

 are similar. Males of Pyranga cestiva 2 are of a far richer vermilion 

 than those frcm Washington, D.C., and resemble more nearly ex- 



1 In this connection see especially the following works : — 

 Allen, Bull. Mus. Comp. Zool., n, No. 3, pp. 233-236. — lb., Do., Vol. in, No. 6, 



p. 114. — lb., Proc. Bost. Soc. Nat. Hist., Vol. xv, pt. 2, Dec, 1872, 



p. 214. 

 Eidgway, Am. Journ. Sci. and Arts, 3d ser., Vol. iv, Dec, 1872, p. 454; Jan., 



1873, p. 39. — lb., American Naturalist, Sept., 1873, p. 

 Coues, Am. Nat., July, 1873, p. 417. 



* In the Colorado province of the United States and the contiguous portions of 

 Western Mexico, is a well-marked geographical race of this species, characterized 

 by much larger size, and purer, though lighter, red colors. In the opinion which 

 they pass upon its merits as a valid race, several authors (see Coues' "Key to North 

 American Birds'' p. Ill, and Maynard's "Birds of Florida." pt. in, p. 85) are at 

 fault, evidently because their conclusions were not supported by the examinations 

 of specimens and comparison of them with the eastern form. Dr. Coues has made 

 this comparison since the publication of his " Key," and the race is consequently 

 recognized in his later "Check List " (p. 23, No. 108a) ; but for the benefit of those 

 who persist in ignoring it, the following facts are presented: (1.) Eastern specimens 



