Of the three species of loons observed on the Arctic Slope, the yellow-billed loon is the least numerous. Owing to its large size this loon is more often taken than either of the others. Eskimos consider its dark, fine grained flesh a delicacy. On the more isolated areas of the Arctic Slope the yellow-billed loon remains common; elsewhere it needs protection.

Additional specimens, especially from the contact zone between the areas of geographical distribution of Gavia immer and Gavia adamsii, are needed in order to decide on the subspecific versus specific status of these two kinds of loons.

Gavia arctica pacifica (Lawrence): Arctic loon.—Specimens, 2: Barrier Lake, NE Teshekpuk Lake, 153°05'40", 70°39'40", 8 ft., No. 30570, ad. female, July 29, 1951; Topagaruk River, 155°48', 70°34', 10 ft., No. 30572, ad. female, July 7, 1951.

On July 3, 1952, between Umiat and Ivashak River, pairs of Arctic loons were on only small and medium sized lakes; on this date they mostly were free of ice whereas large lakes were ice covered and thus unavailable to this species of loon. The use of small and medium sized lakes by this loon may result from the described unavailability of large lakes at nesting time. The tundra, at this time, when nesting has begun, is free of snow except for cornices and deposits in deep gullies. Willows and alders at Umiat on July 3 were without foliage, whereas these plants farther east were in leaf. On July 4, 1951, at two-tenths of a mile south of the Arctic Research Laboratory, a single bird flew over the tundra and onto the Arctic Ocean beyond. It called regularly as it passed overhead. At Topagaruk (July 5, 1951) the pairs of Arctic loons were nesting on the vegetated edges of lakes of medium size. This species of loon constituted less than one per cent of the avian population of the area. A nest of this loon on a promontory between two lakes and within 30 centimeters of deep water was damp, shallow, slightly depressed and held eggs exposed to view. On July 7, the female was killed as she left the nest. The wind blowing offshore drifted her toward the center of the lake. Later, as she reached a point near the opposite side, the male alighted near the dead female and indulged in its courtship display of raising and lowering its head and neck. Swimming around the mate several times he continued to solicit attention from the lifeless form. An hour later we examined the off-shore and found the dead female among the sedges. By this time the male had abandoned its mate and was observed feeding in an adjacent lake. Arctic loons on several adjacent lakes could be heard. The male that had been deprived of its mate, did not respond.

The female weighed 1200 grams. The largest ovum was eight mm in diameter; others were smaller and the smallest were in clusters. On leaving the nest we placed mosses and grasses over it to protect the single egg from the parasitic jaegers. We wished to learn whether the male returned and incubated the egg. On our approach on July 8 he was on the nest but left and swam approximately 200 feet under water before surfacing. On the afternoon of the same day the single egg was cold and unattended. The male was swimming on a nearby lake some 300 yards distant. Two pairs of the Arctic loon were observed swimming on adjacent lakes. On July 9, the male was again incubating the egg.

The Arctic loon calls frequently when flying overhead. The Eskimos were adept at imitating the loon's call and were successful in having the birds respond.

At Kaolak River (July 12-18, 1951), pairs of the Arctic loon used the course of the stream as a flight lane.

On an airflight from east to west between the mouth of the Canning River Canyon and Umiat (July 18, 1952) I noted an increase in the numbers of this loon, especially over the lakes near the Colville River.

Seven pairs and two singles of this species were observed between the mouth of the Avalik River and a point 23.3 miles from the Arctic Ocean when I flew directly from [Kaolak] to Point Barrow. In the above 33 miles of coastal plain, the greatest interval between loons was 9.7 miles, the shortest 1.9 miles, the average 5.9 miles. The last 23.3 miles before reaching the Arctic Ocean, produced no records of the loon. On a lake near the Arctic Ocean, 3.8 miles southwest from Barrow Village, a single pair was observed.

Upon our arrival at Barrier Lake, northeast of Teshekpuk Lake (July 29, 1951), there were two adult and two young Arctic loons at the south end of the lake at a point approximately 300 feet from where we camped. During our stay at the lake, the loons nearly all of the time remained on approximately 1½ acres of water in spite of being disturbed and having their territory periodically invaded by us. Adjacent to the area of the lake used by this family of loons were three small lakes connected by wide channels to Barrier Lake. Other small lakes to the east were connected by smaller channels. The loons preferred to feed in the lakes having larger connecting channels.