Numerous calls of the Arctic loon were heard on the Barrier Lake area. When a person enters the territory of a family of loons, the male makes a sound similar to a courting tomcat. The female responds with a like sound and in addition concludes her call with a high pitched note. When mildly disturbed, low guttural notes are uttered by both sexes, and are continued as a person penetrates farther into the territory of the loons, especially when young are present. In addition to the above-mentioned calls, loons have a ravenlike call, one resembling the cackling of a domestic fowl, and another resembling the bleating of a lamb. The male concerns himself less than does the female with the safety of the family; nevertheless, attempts were noted in which the male endeavored to decoy the intruder and allow the female and young to retreat from the area. The loons react to caribou, if these animals approach too closely to the shore line adjacent to the territory of the loons. On July 30, 1951, pairs of loons were flying over the tundra between Barrier Lake and Teshekpuk Lake. On an airflight from Teshekpuk Lake to Point Barrow (Aug. 4, 1951) I saw Arctic loons as follows: 63 miles from Point Barrow, one; 25 miles from Point Barrow, two; 10 miles from Point Barrow, four. At Chandler Lake (Aug. 12, 1951), a single Arctic loon was frequently heard at the southeast end near the mouth of the Chandler River. In the evening of August 13, the wind changed from the normal southern wind to a cold wind from the north. Thereafter no Arctic loon was detected at the mouth of the river until August 22 when a bird there called at three intervals in the day. Presumably the change in direction of wind caused the fish and the loon to leave the south end of the lake. Arctic loons in other parts of the lake were heard every day from August 8 to August 25 inclusive. On August 19, 1952, when we flew from Umiat to Gavia Lake, the loons seemed to be more restless and more easily disturbed than on our earlier flights. Wariness probably increases as the season advances. On August 20, 1952, through August 23, 1952, six pairs of Arctic loons and 10 old squaw ducks were on Gavia Lake (named after the Arctic loon, genus _Gavia_). These were the only large birds on the lake on these dates. The loons dove as they sensed danger, emitting, before the dive, a single doglike yelp. On September 2, 1952, at 1/2 mile northeast of Barrow Village, we passed an Arctic loon on the beach six feet from the waters of the Arctic Ocean. On the return trip, two hours later, the loon was again seen in the same area, now preening its feathers. As we approached it walked to the water and began to swim through the breakers of the ocean. Snow was falling, telling of the approach of the migratory season for this species.