1920 J Grinnell, Sequestration Notes. 87 



insects or uncover them, but must look for them in plain sight; 

 it must scrutinize a large area of leaf and twig to find enough, and 

 it must avoid duplicating territory that its neighbor Kinglet has scruti- 

 nized. In other words it is of critical need that the individuals of a 

 species whose food is of this nature, and must be gotten in this way, 

 be continually spaced out. over the available food producing terri- 

 tory. Two or more individuals must not follow each other's paths 

 or look over the same ground, at least until there has been time for 

 insect life to move about again. 



With Audubon's Warbler the conditions are very much the same 

 as with the Ruby-crowned Kinglet, save that the forage beat of 

 the former lies, as a rule, in more open trees and bushes, or on 

 the outer surfaces of masses of foliage. The tsip-notes are uttered 

 seemingly for the same general purpose, to keep neighboring indi- 

 viduals from duplicating territory. With both the Warblers and 

 the Kinglets, it is not uncommon in winter to see two individuals, 

 which may happen to encounter one another in the same tree, 

 assume a hostile manner of behavior and tone of voice. The latter 

 consists in each case, of the same sort of expression as the seques- 

 tration note, but uttered with more emphasis. In the case of male 

 Kinglets, there are flashes from the unfurled coronal, and one of 

 the birds quickly puts the other to flight; each is soon pursuing 

 separate forage routes in different directions. 



In the case of the Audubon's Warblers, again, it is quite true that 

 two or more individuals often enter into loose membership in the 

 roving aggregations of birds which travel about the open country 

 in winter and include in their number, bluebirds, certain sparrows 

 and even pipits. And also one often encounters a number of 

 Audubon's Warblers, not in company of other birds, trailing along 

 in the same general direction, with indications that they are trying 

 to keep in loose contact with one another. And here it is possible 

 a shade of meaning in their voices invites collectivity. Indeed one 

 can conceive of a note being both centrifugal and centripetal in 

 meaning, the latter to a given radius, the former beyond. But now 

 our discussion has departed into the realm of speculation. 



In thus assigning the function of sequestration to certain notes of 

 certain birds, the writer has placed confidence in an accumulation 

 of impressions received during a number of years of observation. 



