PACIFIC AUDUBON'S WARBLER 261 



During the summer season the Audubon Warbler keeps mainly to coniferous 

 trees, foraging from 10 to 50 feet or more above the ground. In the Transition 

 Zone and part of the Canadian Zone it shares this habitat with the Hermit 

 Warbler, but at the higher altitudes it is the only warbler present in the ever- 

 green forest. 



Farther north, in Mono County, Calif., James B. Dixon tells me that 

 he found it nesting between 7,600 and 9,500 feet elevation. Referring 

 to the Toyabe region in Nevada, Dr. Jean M. Linsdale (1938) found 

 the Rocky Mountain form in a somewhat different environment : "In 

 the mountains the area occupied by this warbler agreed fairly well 

 with the area covered with trees. Individuals were seen most often in 

 aspens, limber pines, birches, willows, and mountain mahoganies." 

 Angus M. Woodbury (MS.) says of the breeding range of the Rocky 

 Mountain form in Utah : "It summers in altitudes ranging from about 

 7,000 to 10,000 feet and nests in almost any of the components of the 

 forests in those altitudes ; pine, fir, spruce, aspen, or oak." 



In Washington, Audubon's warbler is common and well distributed 

 from near sea level in the vicinity of Seattle and Tacoma up to about 

 8,000 feet in the mountains. Near Tacoma, D. E. Brown showed us 

 some typical lowland haunts of this warbler in the so-called "prairie 

 region." On this smooth, flat land, a fine growth of firs and cedars 

 was scattered about in the open ; the two or three local species of firs 

 were most abundant and were growing to perfection, being well 

 branched down to the ground. 



Spring. — There is a northward as well as an altitudinal migration 

 in the spring. Samuel F. Rathbun says in his notes from Seattle: 

 "Although the Audubon's is of frequent if not regular occurrence 

 during the winter, a migration of the bird through the region is to 

 be noted each spring and fall." Near Seattle the first birds are seen 

 and their song is heard about March 10 to 15, and numbers are seen 

 passing through tip to the latter part of April. "By way of com- 

 parison, in the Lake Crescent section the first are seen about April 2, 

 at the earliest, and after three weeks the last appear to have passed 

 by, as the species performs its spring migration in a leisurely manner." 

 A later wave of migrants passes through Seattle between April 10 

 and 25, probably birds that nest farther north. 



Migration is evident in Utah, for Woodbury (MS.) says: "In ad- 

 dition to its summer residence, it is a common migrant through the 

 state, and a sparse winter resident, mainly at low altitudes. It mi- 

 grates through the streamside and cultivated trees of the valleys, in- 

 cluding shade trees and orchards. The migrations cover a period of 

 about 6 weeks each in spring and fall, usually from about mid- April 

 to the end of May and from mid-September to the end of October, but 

 in different years the waves may be a little earlier or later." 



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