528 ANIMAL LIFE IN TEE YOSEMIT^ 



This warbler forages most especially about the peripheral foliage of 

 the trees. In seeking the sedentary insects lodged on the leaves and in 

 their axils a bird is accustomed to change its post of view by flying out 

 beyond the leafage in a semicircular course toward a new location. This 

 is quite the opposite of the habit of the Lutescent Warbler, for example, 

 which works about within the terminal or crown foliage. The special 

 mode of leaf examination, just alluded to, on the part of the Audubon 

 may be accounted for by the greater proneness of this warbler to indulge 

 in fly-catching. The flight out into the open air puts the bird in position 

 to see and seize with least additional expenditure of energy, passing insects, 

 or insects disturbed from the foliage. This fly-catching habit is often 

 practiced toward evening by several of the birds in near proximity to one 

 another. Then insects are active in numbers about the warm sunlit upper 

 portions of the trees. On these short sorties the bird's wing-beats appear 

 rather weak, and a vacillating manner of flight results. The tail is widely 

 spread, and the patches of white in transverse row near the end show forth 

 plainly. In a word, the Audubon Warbler is the most open-acting, above- 

 board, and the least reclusive, of all our wood Avarblers, 



We were not fortunate in finding any nests of the Audubon Warbler 

 in the Yosemite country. But nests elsewhere are known to be placed 

 many feet above the ground on branches well out from the main stem of 

 the tree and so located that they cannot be readily made out from below. 

 Save when the site is disclosed by a female going to the place, carrying 

 material for the nest or food for the young, much time and energy will 

 be expended vainly in hunting for the structure. On May 17, 1919, in 

 Yosemite Valley, a female Audubon Warbler was seen in the top of a 

 small yellow pine gathering dry needles. She moved off toward a group 

 of large trees of the same kind and was soon lost to view. A similar fleet- 

 ing glimpse was obtained of another bird in Little Yosemite Valley the 

 following day. Bob-tailed young already out of the nest were seen in 

 Yosemite Valley on June 23, 1920. A juvenal bird barely able to fly, 

 and so probably just out of the nest, was seen by one of us at Tuolumne 

 Meadows on July 26, 1915. These dates indicate approximately the extent 

 of the nesting season. 



In the fall, and to a less extent during the winter months, Audubon 

 Warblers are given to traveling in small open flocks, either along with 

 their own kind or mixed with bluebirds. Such an aggregation was seen 

 in some black oaks near Camp Curry on October 7, 1914, there being in 

 it about a dozen Audubons in all. The ' location note, ' tsip, so frequently 

 uttered by each individual in one of these scattering groups, seems to 

 serve well in helping to hold the flock together in its general onward move- 

 ment. Over El Capitan Meadows eight were seen on October 24, 1915, with 



