202 University of California Publications in Zoology [Vol. 12 



tions are preferred doubtless because nearest like their summer asso- 

 ciational habitat. Ten specimens taken, nos. 13705-1371-4. 



There is also in the Museum a skin (no. 4255) taken by J. Gr. 

 Cooper at Fort Mohave, April 2-4, 1861. 



Geothlypis trichas scirpicola Grinnell 

 Tule Yellowthroat 



A cursory glance at the sixteen specimens of yellowthroats obtained 

 shows clearly that as regards size and color two diverse types are repre- 

 sented. Observation in the field showed that there were two categories 

 as regards behavior. And these two assortments, as far as data justi- 

 fies, appear to coincide ; namely, the smaller, grayer and duller birds 

 were quiet, and doubtless migrating, while the larger, more brightly 

 colored birds were in full song, evidently the breeding subspecies. 

 Both forms were found in the densest available cover, the resident 

 birds, however, being always met with in the immediate vicinity of 

 water, while some of the migratory individuals were in quail-brush on 

 the second bottom many rods from the river or nearest slough. It was, 

 of course, impossible to distinguish the forms by appearance in the 

 field : in fact, some of the specimens themselves are only with difficulty 

 and some uncertainty placed in one or the other category. 



After an independent study of the Museum's series of yellowthroats 

 from the western United States, British Columbia and Alaska, I have 

 arrived at the same conclusions as expressed by Swarth (1912, p. 72). 

 These conclusions are that there is no recognizable Pacific coast i - ace 

 (arizela), the name occidentalis applying rightly to all breeding yellow- 

 throats of North America west of the great plains, except those of the 

 San Francisco Bay region (G. t. sinuosa) and those of southern Cali- 

 fornia and Arizona (G. t. scirpicola). 



The breeding males of the Colorado Valley agree with those of 

 southern Arizona and the San Diego district in southern California, 

 and differ from occidentalis in large size throughout, and in brighter 

 coloration. The latter feature consists in a deeper toned yellow below 

 and an extension of this yellow posteriorly to include the abdominal 

 area; in brighter yellow of the erissum ; in the flanks being washed with 

 a darker tone of clay color ; in the dorsum being pervaded with golden 

 yellow instead of being of a grayish cast, as in occidentalis: and in 

 the grayish area on the head bordering the black mask posteriorly 



