164 
THE CONDOR 
Vol. XVIII 
This feeling was measurably heightened by the receipt in November, 
1915, from Mrs. J. W. Wheeler, of Tucson, Arizona, of a freshly killed screech 
owl, secured by her in the vicinity of her home on the outskirts of that city. 
This bird, taken within the range of Otus asio gilmani, was remarkably like 
0. a. cineraceus in appearance, in fact T was unable to see that it differed in 
any way from the one or two examples of that form that were then available 
for comparison. This fact, coupled with Ridgway’s statement of his inability 
to distinguish between the two forms, while tending to shake my previous 
conviction of their distinctiveness, impelled me to look into the matter as 
thoroughly as circumstances permitted. 
During the past winter Mr. A. B. Howell, of Covina, California, has 
devoted several months to field work in the vicinity of Tucson, his collection 
including a series of seven screech owls from that region. These specimens 
he has kindly loaned me. Mr. J. Eugene Law has similarly placed at my dis- 
posal nine Arizona screech owls contained in his collection. These series 
together with the specimens at the Museum of Vertebrate Zoology, give a 
total of thirty skins, from the following points : Chiricahua Mountains, 6 ; 
Huachuca Mountains, 3 ; Tucson and Fort Lowell, 12 ; Phoenix, 2 ; Blackwater, 
2 ; points on the Colorado River, from Fort Mohave to Yuma, 5. 
The most cursory examination of this assemblage is sufficient to show that 
there are two types of coloration exhibited, the darker, clearer gray cineraceus, 
with coarser markings and extension of black areas, and the paler gilmani 
with much finer pencillings. A preliminary division of specimens according to 
color, and without consulting labels, was readily accomplished, but it was a 
somewhat disconcerting result to find in the cineraceus group four skins from 
a point within the habitat of gilmani. These were, the one bird referred to 
above (Swarth coll. no. 10051, female, Tucson, Arizona, November 20, 1915), 
and three others from the Howell collection, all from Fort Lowell, near Tuc- 
son (no. 6205, male, December 26, 1915; no. 6245, female, January 4, 1916; 
no. 6299, female, January 24, 1916). These birds are, as far as I can see, 
indistinguishable in color and markings from specimens taken in the Chiri- 
cahua and Huachuca mountains, and if similar skins from lowland localities 
have been used by others in making comparisons I can well understand why 
the subspecies gilmani might be discredited thereby. 
The point to be made here, however, is that these four are all winter birds, 
taken at the immediate base of a high mountain range, a range that should be, 
and probably is, inhabited by cineraceus. The inference to be drawn is, as I 
believe, that they are individuals whose summer home lies at higher levels, 
that they are, in fact, examples of cineraceus which have migrated downward 
into the range of gilmani. 
Taking the evidence presented by this series as a whole, we have the fol- 
lowing facts : There are two distinct types represented, cineraceus from the 
higher mountains, gilmani from the valleys of southwestern Arizona. Breed- 
ing birds from either region are true to type in their appearance. Extremes 
of the gilmani characteristics appear at points farthest from the known range 
of cineraceus (as at Phoenix and on the Colorado River). At one point at the 
margin of the habitat of gilmani (as I conceive it) there occur in winter exam- 
ples of cineraceus. 
There are certain facts in the distribution of screech owls in Arizona 
which deserve to be emphasized. My conception of Otus a. gilmani is of a bird 
of the hot Lower Sonoran valleys, and of Otus a. cineraceus, as one pertaining 
