18 
THE CONDOR 
Vol. XVII 
Geographically the two forms appear to be absolutely and widely separ- 
ated. Between the mountains of the San Diegan district of southern Califor- 
nia, comprising the habitat of occidentalis, and the mountains of southeastern 
Arizona, where huachucae occurs, lies a stretch of desert several hundred miles 
in extent, forming an impassable barrier between the two. The Spotted Owl 
is a bird of the high Upper Sonoran and Transition zones, and is nowhere 
known to have occurred at any Lower Sonoran locality. Furthermore, it is 
restricted associationally, showing marked preference for heavily timbered 
regions ; such places in the habitats of occidentalis and huachucae being almost 
invariably shady canyons or densely wooded hillsides. Although the Upper 
Sonoran zone extends quite continuously from southeastern Arizona northward 
into central Nevada, and then westward into California, and there might be 
deduced from this a continuity of range of one form with the other, such ar- 
gument would be fallacious, for this region is the extremely arid Upper Sono- 
ran of pinon and juniper, offering nothing to a bird with the requirements of 
the Spotted Owl. 
The species has not so far been found in northern Arizona, nor is it known 
from the east slope of the Sierras, in California, so that altogether it seems 
highly probable that there is an extensive hiatus between the regions inhabited 
by the Spotted Owl in southern Arizona and in southern California. It is to 
be expected, of course, that segregation amid widely different surroundings, 
acting upon a non-migratory animal, would be productive of some variation in 
the inhabitants of the different regions. Furthermore, the observed differ- 
ences distinguishing the few known specimens of the Arizona race from the 
California subspecies, are exactly such as we would expect to find, reasoning 
from analogous cases among other animals of similar distribution. Thus there 
seems to be ample justification for the recognition of the differences existing 
between the California and the Arizona races of Strix occidentalis. As to the 
relationship of the latter, the Arizona bird, to the form of Spotted Owl occur- 
ring southward over the table land of Mexico, that is another matter, to be de- 
termined by future study of more material than is now available. 
As stated above, the opportunity I have enjoyed of making the compari- 
sons herein recorded, is primarily due to the consideration of Dr. Louis B. 
Bishop, in loaning me his Arizona specimens. Of the other skins examined, the 
type specimen of 8. o. huachucae was borrowed from the California Museum of 
Vertebrate Zoology, where it is on deposit as part of the Morcom collection; 
while the examples of 8 . o. occidentalis are all either from the collection of the 
Los Angeles Museum of History, Science, and Art, or of the several individuals 
who have their collections on deposit in that institution. Their names appear 
in the appended list of specimens, and to each one I wish to express my appre- 
ciation of the privilege I have enjoyed. 
Accompanying is a list of the specimens upon which this study is based. 
The examples of 8. o. occidentalis are all from points in the San Diegan district, 
southern California; of 8. o. huachucae, from southeastern Arizona. For the 
sake of the measurements 1 have included several skins not actually handled 
at this time. The data pertaining to these is copied from my previous paper on 
I he species, before cited, and these skins, during the preparation of that paper, 
were carefully compared with the one example of huachucae then available. 
