PILEOLATED WABBLEBS 541 



by a few days. By the middle of May their headquarters are established, 

 and -with the coining of June nests are to be expected. After the young 

 are abroad some of the birds wander above the boundary of the breeding 

 zone. Two, for example, were seen on Mount Clark at an altitude of 

 10,500 feet on August 22, 1915. Our last record of the species for the 

 west slope was made August 28, 1915, when an immature bird was taken 

 at Washburn Lake. The species occurs still later, however, for Mr. Joseph 

 Mailliard (1918, p. 19) states that in 1917 it was noticed up to Sep- 

 tember 22. 



The Alaska Pileolated Warbler is a migrant along both sides of the 

 Yosemite region. Near Mono Lake the first (pileolata) in 1916 was seen 

 on April 29. Thereafter they continued in exddence until May 31, and it 

 is possible that some of the birds remained there to nest. Only a few 

 were noted on the west slope ; one of those seen was obtained near Lagrange 

 on May 8, 1919, The time of the return migration of this race has not 

 yet been determined for the Yosemite region. Pileolated warblers (sub- 

 species undetermined) were noted in Yosemite Valley from August 25 

 until October 4 in 1920 (C. W. Michael, MS). 



The Pileolated Warbler, whichever the race, may be known at a glance 

 by the cap of black on the top of the head (pi. 9^;). Both males and 

 females, adult and young, have some of this marking. It is largest and 

 most intensely black in adult males. In most warblers the females lack 

 certain of the striking (and to us useful) markings worn by the males, 

 but here the two sexes are closely alike. The present species shows no 

 other contrasting color features ; its plumage is yellow, tinged on the back 

 with green. In one of the races (chryseola) the color of the forehead has 

 an orange hue. 



Pileolated Warblers do the most of their foraging within 6 feet of the 

 ground and practically never ascend far into trees even to sing. They 

 keep within the cover of the lower stratum of foliage and are therefore 

 only to be caught sight of momentarily. The birds are noted for their 

 habit of darting out after flying insects ; indeed one book name of the 

 eastern relative of the pileolated is "black-capped fly-catching warbler." 

 Of all our other warblers only the Tolmie is likely to be found in the 

 same cover inhabited by the Pileolated Warbler. (See fig. 56.) The Tolmie 

 often forages out into the drier chaparral, whereas the present species 

 adheres closely to damp situations, either over boggy ground or else within 

 a few yards of a stream. In favorable country, pairs of Pileolated 

 Warblers may occur as frequently as eight or even more to the linear mile. 



The song of the Pileolated Warbler is far less shrill than that of the 

 Yellow Warbler and is less clear and more mechanical than that of several 

 other warblers. The syllables are given all on about the same pitch and 



