1910] Tracy: White Markings in Birds. 295 



THE PEOBLEM DISCUSSED FOE BIEDS OF THE OPEN. 



The list shows five families that carry white markings, as 

 against two families that do not. Of the twenty-six species or 

 subspecies that carry them, all but three are to be classed as 

 flocking birds; and even these are unquestionably gregarious to 

 a marked extent. They may follow each other serially from 

 place to place, as the cactus wren {Heleodytes hrunneicapilhis) 

 and the sage thrasher {Oroscoptes montanus) , or they may flock 

 for a limited season, as the vesper sparrow {Pooecetes gram- 

 ineus). The list contains the most perfect types of flocking birds 

 in the whole order, such as the meadow pipits of the genus 

 Anthus, and the horned larks {Otocoris alpestris), the lark spar- 

 rows (Chondestes grammacus), and all the juneos. Taken as a 

 whole the white-marked group is unquestionably a flocking series. 

 The bearing of this on the problem of white markings in birds is 

 made clear by a comparison with the second list in which all but 

 the species of two genera, Leucosticte and Dolichonyx, are seen 

 to be of a non-flocking, skulking type, exemplified by the grass- 

 hopper and Savannah sparrows. Of these two exceptional genera 

 the leueostictes are birds of the Boreal Zone exclusively, feeding 

 on wind-blown insects at high altitudes; themselves conspicuous 

 through their dark coloration and, by virtue of their Alpine- 

 Arctic habitat, escaping most of the birds of prey. In short, they 

 are of an environment altogether different from that commonly 

 referred to as "open ground" in the sense of prairie and plains, 

 and may be eliminated from the comparison. Dolichonyx, the 

 bobolink, on the other hand, is a bird in its southern habitats 

 palustrine, and only in its breeding range a bird of the meadows, 

 where it displays the qualities of the second group, and is, in 

 the case of the female, like them unmarked. The coloration 

 of the male in breeding plumage evidently corresponds to that 

 of the marsh blackbirds, to which it is closely allied. Our second 

 list, then, if it be found to contain no flocking birds but the two 

 just mentioned, is a striking proof of the absence of white 

 markings in birds of the open ground that do not flock. 



For an interesting exhibition of correspondence between habit 

 and coloration, we turn to the grasshopper and Sandwich spar- 



