574 BULLETIN 203, UNITED STATES NATIONAL MUSEUM 



though it varies among and in individuals as widely as does the word-form. 

 The timbre of this song was hardly typical : it was unusually loose and liquid. 

 The utterance was comparatively slow. 



Samuel F. K-athbmi writes that in Washington the western yellow- 

 throat sings from the time of its arrival, during the last week of April, 

 until nearly the end of July. 



Like its eastern relatives, the western yellowthroat has a character- 

 istic flight song which has been noted by various observers but I have 

 seen no published accounts of the details of the performance. 



Enemies. — The western yellowthroat is frequently parasitized by the 

 cowbird, and several writers claim that it is one of the most frequent 

 victims in their respective localities. The records range from Colorado 

 to Utah, the latter probably referring to the sagebrush cowbird. In 

 California this yellowthroat has been reported as being parasitized by 

 the dwarf cowbird. 



While the yellowthroat resides in a habitat where it would not be 

 expected to be molested, nevertheless, according to various reports, it is 

 often a victim of predatory birds. W. L. Finley (1907) relates an 

 experience in which a Cooper's hawk attempted to strike the birds he 

 was observing. 



Migration. — The dates of migration of the western yellowthroat 

 seems to vary greatly in different parts of the west, depending on the 

 altitude, climate, and temperature of the regions traversed. W. W. 

 Cooke (1904) states: "The birds arrive at just about the same time — 

 second week in May — on the plains of north-central Colorado and at 

 Great Falls and Columbia Falls, Mont., the latter place almost 600 

 niiles farther north, but enjoying at this period of the year an equal 

 degree of warmth with the Colorado plains. But almost a month ear- 

 lier than this, southern British Columbia is reached by the yellow- 

 throats that wintered in the warm valleys of California lying as far 

 north as the plains of north-central Colorado which during the winter 

 season can support no warbler life." 



It is difficult to follow the migration of the western yellowthroat, as 

 it passes through regions where it is resident and where other sub- 

 species are also resident. In Arizona it is a common migrant in 

 April and May (throughout May at Shiprock, N. Mex.) and has been 

 reported at Rinconada May 5, 1904. It has been recorded as late as 

 May 10 at Ortez, Sonora, Mexico. Spring dates in California are: 

 Colorado River Valley and San Clemente Island, March 23 ; Pasadena, 

 March 25; Berkeley, May 21; and Yosemite Valley, May 25. The 

 western yellowthroat arrives in Oregon during April, the earliest date 

 for Jackson County is March 22 and the earliest date for Lake County 

 is April 9. In Washington it reaches Seattle April 17-21 ; Hoquiam, 

 April 27 ; Ocosta, April 30 ; Tacoma, April 6-12 ; and Yakima County, 

 March 29 



