1907] Beebe: Geographic Variation in Birds. 9 



tremes of color being in sharp contrast to each other. The black 

 cervical band is very wide. The greater wing coverts, instead 

 of showing vague slate-colored markings, are crossed by clear- 

 cut transverse bars, while the doubly crescentic black bars on 

 the feathers of the under parts are twice as broad in the Jamaica 

 bird as in the typical northern bob-white. 



Black predominates on the inner tertials and the buff edge- 

 ings of these feathers are wide and very intense. The feathers 

 of the back and tail coverts are dark, while the tail feathers 

 themselves are almost black. Everywhere on the body and wings 

 the red color, where not replaced with black, is deep and in- 

 tense, a rich rufous much as in Colinus cubanensis. The wing 

 of this bird measures 4.25 inches and the tail 2.25 inches, 

 these measurements being considerably less than in birds from 

 the north. 



The quail flourished on the island until the mongoose was in- 

 troduced, an animal which increased so rapidly as almost to 

 exterminate the terrestrial mammal and bird fauna. The result 

 of this is that to-day the quail are very rare, there being but 

 two or three small covies scattered over two restricted districts. 

 A recent observer estimates the total number of birds on the 

 island at not over 70. 



Although dark coloring in southern humid regions is often 

 accompanied by a decrease in size, rarely by an increase, there 

 is, as I think my experiments on Scardafella show, no necessary 

 intimate correlation between the two phenomena. That of size 

 may indicate, as Dr. Allen suggested thirty years ago, the course 

 of adaptive radiation; the larger forms representing the hypo- 

 thetical center of distribution. But size may or may not be sig- 

 nificant of long existing conditions (cf. the Porto Santo rabbits, 

 p. 7), while, as we shall see, geographical variations in color, 

 even after long continued exposure of generations to an extreme 

 of climate (Scardafella inca, in Mexico and Arizona) may prove 

 to be of the most plastic and evanescent character. 



Part II. — Dichromatism. 



The more or less regular occurrence of black or dark-col- 

 ored individuals among wild birds is known in many instances. 

 From these I shall select a few of the more significant. The Old 

 World snipe Gallinago gallinago ranges over Europe, Asia and 

 North Africa. Fifty-five melanistic specimens are known in col- 

 lections, so-called G. sabinii, of which thirty-one were taken in 

 Ireland, twenty-two in England and one each in Scotland and on 



