1907] Beebe: Geographic Variation in Birds. 25 



Brazilian specimen, 100 per cent, of the doves show white-tipped 

 third rectrices, and, allowing for individual variation in the 

 Nicaraguan specimen, the ratio of variation is the same as in 

 the fourth pair of feathers; the Venezuelan birds showing the 

 greatest amount, and the Brazilian specimen a reduction approx- 

 imating the area of the Honduras doves. 



As the extreme development of white we find the second 

 pair of rectrices distinctly tipped in several of the Venezuelan 

 specimens, and the dove described from Margarita Island by Dr. 

 Richmond is said to have white on the terminal parts of five pairs, 

 the central tail feathers alone appearing solid brown. 



With all this general uniformity of result, the great indi- 

 vidual variation should not be lost sight of. In two birds from the 

 same locality, collected within a few days of each other, the varia- 

 tion may be extreme. In one the demarcation of dark brown and 

 white in the rectrices is sharp and clear cut; in the other the 

 colors merge so insensibly into one another that it is difficult to 

 tell where to put the millimeter measure. 



Of the entire body plumage, the under tail coverts perhaps 

 show this individual variation to the greatest degree. If there 

 is a distinct terminal mark of black, the feather is apt to be white 

 elsewhere, but the reduction or absence of this mark is often 

 accompanied by an infusion of pale dirty-brown from the base 

 of the rhachis, extending along the shaft line and sometimes dis- 

 coloring two-thirds or more of the whole vane. This condition, 

 however, is confined to the more northern birds, the colors of the 

 South American doves being remarkably distinct and clear-cut. 



In the Arizona and Texas birds there is also considerable 

 variation in the pigmentation of the right and left wing and tail 

 feathers, while in the tropical specimens almost perfect bilateral 

 symmetry is found. 



B — The Effect of Humidity on Scardafella inca (Less.). 



When typical specimens of Scardafella inca — ^the Inca or 

 Scaly Dove, from Arizona or Mexico are confined in the humid 

 atmosphere for at least six months before the annual fall moult, 

 there is a noticeable change in the new feathers ; a slight increase 

 in the amount and intensity of the dark tips, uniformly over the 

 whole body, and a slight blackening of the primaries and rec- 

 trices. One individual, even at this first moult, shows a condi- 

 tion adumbrative of the whitened wing coverts which are so con- 

 spicuous a feature of the next moult. This bird closely re- 

 sembles the Scardafella inca dialeucos type. At the second fall 



