206 — Vol. XXIV 
DISTRIBUTION OF MOLOTHRUS ATER IN CALIFORNIA 
WITH THE DESCRIPTION OF A NEW RACE 
By DONALD R. DICKEY and A. J. VAN ROSSEM 
URING the late spring and summer of 1920, the writers took a series of 
ecowbirds at Buena Vista Lake, Kern County, California. Pressure of 
other work prevented careful diagnosis at the time, and since birds of that 
region had previously been referred to Molothrus ater obscurus, that name was 
tentatively applied to these specimens. On further examination this series 
showed such a definite departure in characters from those exhibited by a large 
collection of obscurus from the Colorado Desert and adjacent regions, as to 
make a thorough analysis of the status of cowbirds in California seem advisa- 
ble. 
With this end in view, we have assembled or examined all of the material 
available in the Museum of Vertebrate Zoology and the Museum of ITlistory, 
Science and Art, together with many individual specimens gathered from pri- 
vate sources. Our thanks are due not only to those in charge of the ornitholog- 
ical collections of the institutions mentioned above, but also to the several pri- 
vate collectors who have so courteously placed their material at our disposal. 
The resultant data has served to emphasize the fact that much remains to 
be done in the way of systematic collecting even in a State that has been as 
thoroughly canvassed as California. In the present instance there is adequate 
material from southern California, north to Mono Lake on the east, to Merced 
County in the San Joaquin Valley, and to Oxnard, Ventura County, on the 
Pacific Slope. North of these points we have been able to trace only a single 
specimen from the Modoe region, a stray migrant from the Farallon Islands,. 
and two non-breeding birds from Santa Barbara County. Cowbirds are known 
to occur in fair numbers at various intermediate points, but specific records 
seem unexpectedly scarce and specimens lacking. 
A general impression seems to have sprung up that cowbirds have only 
recently invaded California. It is unquestionably true that their numbers have 
mereased greatly during the past few years, but in our belief this is due simply 
to natural increment rather than influx, and is adequately explained by the 
increasingly favorable conditions that have inevitably resulted from the present 
extensive development of dairying, truck-gardening, and irrigation projects in 
general. So far as we can determine there is no reason to suppose that Cow- 
birds, in small numbers, have not always been residents of the area. J. Grin- 
nell(’) and Edward Wall(*)have already made some very pertinent remarks 
on this subject, 
Molothrus ater obscurus (Gmelin) 
Dwarf Cowbird 
Range in California: Southern California, from the Arizona line west to 
San Diego; north over the Colorado and Mojave deserts to Death Valley, the 
Panamint Mountains, and Independence, Inyo County; north through the San 
Diegan district to the vicinity of Ventura and, in winter at least, to Goleta, 
Santa Barbara County. Specimens examined (approximately 150) from the 
( 
( 
ys Univ. Calif, “Publ, Acoli s,, 1909s sop. 27a oeae 
yy Condor. 21, A919. son eZ09) 
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