522 ANIMAL LIFE IN THE TOSEMITE 



The song notes of the California Yellow Warbler are shriller than those 

 of any of our other warblers, and, indeed, are exceeded in height of pitch 

 by the notes of only a very few birds. This feature alone is often sufficient 

 to identify the song. Syllabification can do little more than indicate the 

 theme of the song, for the notes are well above those of the human voice. 

 Wee, wee, wee, sit, sit, sitsitsit, sieu, is one of our renderings; and chee, 

 chee, chee, chee-e-e-e-e-e-er another. The call note is a loud chip or tsip. 

 Song is not heard often after the first part of July, but there may be a 

 partial revival of singing in the latter part of August just before the birds 

 depart for the season. 



Yellow warblers like many other birds have definite forage beats which 

 they traverse repeatedly through the day. This was well illustrated by 

 observations on a bird of this species seen at Chinquapin in mid-May, 1919. 

 A small black-oak sapling had grown up through the sea of chaparral near 

 our camp and from time to time this tree would be occupied, momentarily, 

 by a California Yellow Warbler. The bird always arrived from a certain 

 direction (coming from another similar station) and upon departing went 

 to still another definite tree situated about 50 yards distant. 



Nesting with the California Yellow Warbler begins soon after the birds 

 arrive in the region, our earliest record being for May 29 (1911) ; on this 

 date, in Yosemite Valley, a female was flushed from a nest containing four 

 eggs. Two nests seen on June 5, 1915, at Smith Creek, east of Coulterville, 

 each contained young a few days old. Nest construction in each of these 

 instances must have commenced in the middle or early part of May. June 

 marks the height of the nesting season for the Yellow Warblers here; in 

 this month the greatest number of nests comes to attention. An adult was 

 seen feeding young recently emerged from the nest, on July 24 (1915) 

 in Yosemite Valley. This instance marked about the close of the nesting 

 season. The one nest found east of the mountains (near Williams Butte) 

 was only under construction on June 23 (1916). 



Yellow warblers nest abundantly on the floor of Yosemite Valley. Some 

 of the nests are in growths close to water, whereas others are located in 

 brush tangles or other rank growths back some distance from the streams. 

 A nest found June 7, 1915, may be taken as fairly typical. It was 52 

 inches above the ground in the crotch of a forking stem of a chokecherry 

 which grew in a clump of the same plant, and was shaded by a black oak. 

 As usual it was higher than wide outside, being 31/2 inches in height by 

 3 to 31/4 inches in diameter. The cup-like cavity was 1% inches across 

 at the top and the same in depth at the center. Shreds of bark and flat 

 plant fibers were the principal materials used in construction, the lining 

 being of horsehair and a few feathers. 



