AUDUBON WABBLEB 525 



During the winter months the birds are entirely gone from the high 

 country. In this season the species occupies most of the hill and valley 

 country lying below the level of regular snowfall. The district from 

 El Portal westward to Snelling and Lagrange is tenanted by numerous 

 Audubon Warblers from October until early April. In Mono Valley east 

 of the mountains there are, in all probability, no Audubon Warblers what- 

 ever present during the long season of snow and storm there. 



The migratory movements of the Audubon Warbler are but imperfectly 

 known. Birds of this species begin to appear in the lower altitudes in 

 late September or early October, but at this time many are still in the 

 mountains where they continue until late in October. Through September 

 there are droves of Audubons in the trees and brush on the east slope of 

 the Sierras. Doubtless these are mostly birds from stations to the north 

 en route to their wintering grounds in southern California and beyond. 

 The return movement of the species is accomplished in April, and by 

 early May the western foothills are practically cleared of the species. It 

 yet remains to be learned whether the birds which leave the Sierras in the 

 fall go directly westward into the foothills, to remain there for the winter, 

 or whether they move southward and individuals from northern localities 

 migrate into the foothill territory. 



As to numbers, in the summer time our censuses show one to two sing- 

 ing birds during an hour of ordinary walking through favorable territory. 

 About 10 were noted in 4 hours on the floor of Yosemite Valley May 33, 

 1915. Eleven were noted in 5 hours in the vicinity of Porcupine Flat on 

 June 27, 1915. And 3 were recorded in 3i/^ hours at the head of Lyell 

 Caiion on July 16, 1915. After the young are out, better scores are to b^ 

 made ; 13 were noted in 3^/2 hours along the Tenaya Trail from Tenaya 

 Lake down to Mirror Lake, July 30, 1915. Fully 50 were seen in 6 hours 

 between Vogelsang Lake and Mono Pass on September 7, 1915. At Gem 

 Lake, on September 13, 35 were noted in 2 hours of intensive hunting, 

 this warbler being then the most plentiful bird there. In 1920 Audubon 

 Warblers were abundant in Yosemite Valley during the first three weeks 

 of October; then a sudden decrease in numbers was noted, and the species 

 disappeared on October 28, save for a solitary individual noted on Novem- 

 ber 3 (C. W. Michael, MS). 



More differences in plumage are shown by the Audubon Warbler 

 according to sex, age, or season, than by anj' other common bird of the 

 Yosemite avifauna. Upon hatching, the young are sparsely clothed with 

 a grayish white natal down. While still in the nest the juvenal plumage 

 is acquired. In this the body feathers are sharply streaked, while the 

 flight feathers are closely similar in color and markings to those of the 

 adult. In these first two plumages the sexes look alike, but upon the 



