1910] Tracy: White Markings in Birds. 291 



There are birds that appear to depend almost entirely upon 

 directive calls for keeping together ; they have become habituated 

 to feeding in close and uninterrupted cover where they see other 

 birds only at close range, or very seldom at any great distance. 

 Obviously they must keep within hearing, or be lost to their 

 companions. Sound-clues are sufficient in their case. This is 

 true of the bush-tit (Psaltriparus minimus calif amicus) , some 

 warblers, and nearly all the wrens. These are birds of plain 

 colors, for the most part, and without white patterns of any sort. 



Among arboreal birds of open feeding range that are con- 

 stantly exposed to view, diiferent conditions obtain. Call-notes 

 are used, but glimpses of other birds in flight may be just as 

 useful for purposes of direction, since such glimpses are 

 frequently to be had. Sight plays a part of corresponding 

 importance in the economy of bird-movement — to some extent 

 replaces sound as a means of recognition. 



As there is in the general coloration of open-ranging birds no 

 response to the need of some rapid and easy means of recog- 

 nition, and as the special color patterns that have heretofore 

 been regarded as serving that purpose are now being claimed as a 

 part of "concealing coloration" (A. H. Thayer, 1909), it might 

 appear that the category of directive markings is soon to lose its 

 status altogether. But general coloration is seen to be normally 

 protective, for birds that need protection; and as for the special 

 patterns, even a satisfactory demonstration of their "oblit- 

 erative ' ' effect does not warrant the conclusion that such is solely 

 or mainly their effect in all cases. 



For a discussion of the "disruptive effect of color patterns" 

 the reader is referred to G. H. Thayer, 1909, pp. 77-79, and to 

 A. H. Thayer, 1909, pp. 562 et seq. The evidence here offered 

 of their value as revealing characters, must not be regarded as 

 contradicting anything but the application of the "concealing" 

 principle to birds in flight. 



During the month of February the writer had under observa- 

 tion a flock of fifteen meadowlarks (Sturnella neglecta), which 

 foraged in vacant lots and fields within the city limits of Berkeley. 

 They were well spaced while feeding, and when disturbed some 



