GREAT GRAY OWL. Scotiaptex nebulosa nebulosa (Forster)

Field characters.—Size very large (largest of our owls); length nearly two feet, expanse four feet and a half; head big and round, without ear tufts; eyes yellow; tail relatively long. General color grayish brown with dull mottlings and streakings of white; no conspicuous white throat patch. (See text fig. 39h and pl. 43c). Voice: A deep reverberating whoo, given at irregular intervals.

Occurrence.—Probably permanently resident. Found by us only in the fir woods of the Canadian Zone. Definite stations: 7400 feet altitude, within one mile south of Ostrander Rocks; 7900 feet, within one mile north of Indian Rock. Seems prone to be active during the daytime, but keeps within thick timber.

The discovery of the Great Gray Owl in the Yosemite section was one of the notable events in our field experience. And what was most surprising was the fact that the bird was apparently quite at home, and nesting. No previous record of the breeding of this northern species of owl south of Canada is known to us, and its occurrence even as a winter visitant within the northernmost of the United States is not frequent.

On June 18, 1915, we were camped to the south of Yosemite Valley on the Glacier Point road within two miles south of Ostrander Rocks. A long trap-line beginning at camp led up the gentle slope toward the latter landmark and through a fine forest of red fir. During inspection of this line on previous days we had distant glimpses, morning or evening, of a large bird in silent flight among the trees. On the day of discovery, however, the diminutive kinglet pointed the way and really deserves all the credit. From a distance through the forest came the low but insistent wer-rup, wer-rup, wer-rup of a Ruby-crown, its unmistakable note of anxiety. The clue was traced by the expectant naturalist to a tall fir, out from near the summit of which there presently flew a great owl. The bird alighted at the top of a Jeffrey pine close at hand where it was shot and wounded. As it fell to the ground it gave several deep-pitched whoo's. At this, another owl appeared in flight from one fir top to another and was also obtained.

We wanted to photograph it, so the wounded bird was taken back to camp alive. Its huge facial discs (pl. 43c), each centered by a great yellow irised eye, its snapping bill, and its spasmodically clenching claws, all contributed to profound respect on our part in the necessary handling incidental to taking the pictures.

On succeeding days a careful search of the vicinity was made, and a large nest of sticks, which, it was thought, belonged to the owls, was found one hundred feet above the ground on the close-set branches of a fir next to the trunk. But no close examination of it was made. On June 19 in the same stretch of woods the deep notes of an owl were heard three times repeated, but the bird could not be located. This time the kinglets failed us.

The two specimens obtained proved to be male and female, probably a mated pair. As is usual with owls the female was slightly the larger, measuring: total length 595 millimeters (nearly 2 feet); expanse of wings 1370 millimeters (4-1/2 feet). The male measured: length 580 millimeters; expanse 1350. In both birds the iris was bright straw yellow; bill greenish becoming yellow toward tip; claws lead-color darkening toward tips. The stomach of each bird was empty.

As an indubitable indication of breeding during the current nesting season, the female was found to have a large bare tract on the lower surface of the body, including the belly and insides of the thighs, from which the larger feathers had all been removed. Associated with this condition, directly beneath the bare skin, were layers of fat, though the bird was otherwise lean. As is well known, many birds show, during the nesting season, the same or similar adaptations for the better performance of the functions of incubation. The male Great Gray Owl lacked any such modifications, and we may infer that in this species the female alone performs the duty of incubation. The reproductive organs of both the birds indicated that the time of actual egg laying was long past. It seems more than likely that a brood of young had been reared in the vicinity and, approaching maturity, had scattered out through the adjacent woods.

On July 1, 1915, a Great Gray Owl was met with on the old Snow Flat trail, a mile or so north of Indian Rock. When first seen it was perched on a low limb of a lodgepole pine not over 10 feet above the ground. Two juncos in the vicinity were in spasms of excitement. The owl, taking alarm, flew to a higher branch of a neighboring tree, and thence made off into a dense stand of red firs. Its species was easily recognized by its great size, dark gray plumage, big round head without ears, and by the slow flapping of its broad rounded wings. No note was given by this bird. This was at 1:30 P.M. As far as our observations went, this species would seem to be more active by daylight than other owls such as the Pacific Horned Owl.

In Aspen Valley, on October 13, 1915, at 7:30 P.M., an owl note, supposedly of the Great Gray, was heard; but it proved impossible to verify the identity. Near Tamarack Flat, on May 24, 1919, similar notes were heard but the birds were not seen. Notes of certain individual Band-tailed Pigeons proved enough like those of this owl to cause confusion until the authors of the notes were actually seen to be pigeons.