+Sterna paradisaea+ Pontoppidan: Arctic tern.--Specimens, 11: 7-1/2 mi. S and 7 mi. W Point Barrow, 156 deg.49'15", 71 deg.16'52", sea level, 2, Nos. 31315 and 31318, ad. male, Sept. 6, 1952; NE Teshekpuk Lake, 153 deg.05'40", 70 deg.39'40", 8 ft., 3, Nos. 30750-30752 including 2 ad. males and 1 ad. female, Aug. 1, 1951; Topagaruk River, 155 deg.48', 70 deg.34', 10 ft., 3, Nos. 30753, ad. female, July 7, 1951, and 30754, ad. male, July 9, 1951, and 30637, male, July 9, 1951; Kaolak River, 159 deg.47'40", 70 deg.11'15", 30 ft., 3, Nos. 30747-30749 including 2 ad. males, July 14, 18, 1951, and 1 ad. female, July 12, 1951. Adult males and females prepared for specimens at Topagaruk (July 7, 9, 1951) showed signs of molting, especially in the primary wing feathers. Three adult males averaged 92(87-93) grams in weight (the largest male collected on the Arctic Slope was from Teshekpuk Lake on August 1, 1951, and weighed 106 grams). The testes of these males averaged 4.2 (3-5) mm in length (in late autumn testes recede to approximately 1.0 mm in length). Two females from the same place and shot on July 7 and 12, weighed 99 and 100 grams. The average diameter of the largest ovum was 2.0 mm and the longest ovary was 6 mm. At Kaolak River (July 12-18, 1951) an adult hunted day and night over shallow water on a sand bar approximately 500 yards from its nest. Water from lakes in an abandoned section of the river valley caused a creek to flow at night into the river. In the day ephemeral pools were formed because more water evaporated or sank into the sands. As pools were formed, small fish one inch in length were trapped. Before the pools disappeared, the tern captured all these fish. One of the terns that had been feeding on these fish flew out over the upland tundra approximately 500 feet from the river valley. This tern dove at us twice and then returned to the river valley and its nest some 800 feet away. The nest of this bird was on one of three islands in a small lake. The nesting island was three square yards in area and had been built to a height of four feet above the level of the mainland by many years use of the island. The nest was within 30 feet of a nest of a red-throated loon, which was accepted in the territory of the tern without molestation. Northeast of Teshekpuk Lake (July 29-Aug. 4, 1951) a pair of terns had young on a small island in a chain of lakes opening into the south end of Barrier Lake. The adults hunted small fish along the south end of Barrier Lake but especially in small lakes surrounding their nest. These birds seemed to be the only terns nesting on this large lake. As food was plentiful, available nesting sites may have governed the size of the tern population.