Golden eagles daily hunted prey along ridges where Arctic ground squirrels (Spermophilus undulatus) were abundant, for example, at Wahoo Lake (July 3-12, 1952) and at Porcupine Lake (July 13-18, 1952). This species of eagle hunted also in areas where marmots (Marmota caligata) were abundant, as on the slopes adjoining Lake Peters. There (August 6, 1952) three eagles soaring at 3800 feet elevation south of the mouth of Chamberlin Canyon elicited from each of four marmots three warning calls. Thereafter the marmots remained silent until the eagles had left the area. One eagle that consistently hunted (July 17, 1952) on the lower slope of Mount Annette along the Canning River was three times harassed by two ravens.
At the south end of Lake Peters (July 31, 1952), a pair of adult eagles soared along the slopes of Mount Mary approximately 1000 feet above the lake. Twenty minutes later these birds flew by camp at the base of the mountain. On August 2, at 8:00 P.M., two birds, one a large dark adult and one a bird of the year (?) dropped with partly closed wings from high on the east side of the lake to an undisturbed meadow on the west side. After circling the meadow once, the two birds spiralled upward to approximately 4500 feet elevation in one steep canyon, leveled off and after gaining the head of the next canyon, plummetted down to the base of the mountain some 1500 feet below. The high-speed flight continued across the ridge to the mouth of the next canyon where they circled twice and then soared upward to repeat the act. The objective probably was to surprise and prey upon small game at the mouths of each canyon. On August 13, the eagles were still in the area at the south end of Lake Peters in spite of an abrupt seasonal change; snow and rain increased and the temperature dropped.
On August 15, a Dall sheep (Ovis dalli) crossed the canyon from Mount Mary to the mouth of Chamberlin Canyon. As the sheep reached the east side of the canyon an eagle flew across the canyon and alighted approximately 150 feet from the sheep. A large group of small birds immediately harassed the eagle.
Two eagles fed on a dead caribou on a delta on the east side of Lake Peters. Eagles were noted every day at Lake Peters from July 31 to August 15 inclusive.
Falco rusticolus obsoletus Gmelin: Gyrfalcon.—At the southwest corner of Barrier Lake on July 29, 1951, a gyrfalcon sat on a bank 10 feet above the water level. A dead Arctic tern was on the beach only 90 feet away and visible to the gyrfalcon. When approached to within 250 feet, the gyrfalcon, rather than flying north over the lake and lowlands, flew south across the upland tundra. On August 3, on the edge of the upland tundra approximately 3½ miles farther east a gyrfalcon ate a Sabine's gull—a bird of the year. Its feathers had been plucked and only the stomach and intestines remained. The gyrfalcon left the feeding area when approached to within 450 feet and, as did the other gyrfalcon, flew south over the upland tundra rather than over the lowlands of inundated sedges. On July 4, one gyrfalcon sat on a promontory at the south end of Barrier Lake. This bird flew south.
At Umiat (Sept. 1-5, 1951) a gyrfalcon each day hunted the same areas of marsh in the river valley where tundra voles (Microtus oeconomus) were numerous and along the side of the valley where ground squirrels were common. On several occasions, this bird hovered 30 feet up and inspected us. This confidence was in contrast to that of the gyrfalcons at Teshekpuk Lake; they evaded us by leaving the ground several hundred feet away and flying out of sight.
Westley Redhead told us that a gyrfalcon was at Umiat as early as the latter part of May, 1952. We saw them there on September 1 and 2 in the same year. Gyrfalcons feed on ptarmigan in the river valley and on ground squirrels and small birds on the uplands by striking their prey on the ground. These falcons fly like prairie falcons and are of the same nervous disposition.
Falco peregrinus anatum Bonaparte: Peregrine falcon.—A nest was found on June 27, 1952, on the south slope of Mount Umiat approximately 225 feet above the Colville River, 40 feet from the top of the cliff and 30 feet west of the top of the mountain. The nest, three feet in depth at the front, two feet in depth at the rear, and 2½ feet wide was made of sticks of many years accumulation and was placed on a pinnacled platform 12 feet high. The nest contained one infertile egg and two others in which embryos were approximately one third developed. The female remained near us the one hour that we were in the area. She flew back and forth in front of the nest terminating each flight in an upswing arc and occasionally rested on top of the ridge to the west. She dove at us but never came closer than 10 feet before swerving upward. The male was not present. In a canyon 1⁄5 mile northeast of the nest two dead ptarmigan were at the edge of a willow cotton-grass swale. A nest of a peregrine falcon used three years before was 1 7⁄10 miles east and 1 7⁄10 miles north of Umiat. The nest was eight feet up on the face of a cliff 13 feet in height and easily accessible to either fox or wolf. Along the Colville River the falcon feeds on small shore-birds and other small birds.
Falco columbarius bendirei Swann: Pigeon hawk.—On a benchland between Chandler Lake and mountains to the west on August 12, 1952, a pigeon hawk hunted back and forth across a meadow, fearlessly inspecting us from distances of 20 to 30 feet as it searched the meadow for food. This falcon systematically searched those areas where longspurs were known by us to be most frequently found. Twice it flushed Lapland longspurs and darted at them but without success. Of the four pigeon hawks at Chandler Lake three were moving south and one was moving north down the canyon. We saw this species at Chandler Lake also on August 17, 20 and 21, 1951, and at Driftwood on August 27, 1952.
Approximately 1⁄10 mile north of James Robert Lake (Aug. 8, 1952) a pigeon hawk was harassing five ravens that were feeding on a dead caribou. This falcon flew back and forth above the ravens.