A single parasitic jaeger was noted at Chandler Lake on August 10 and one on August 11, 1951. At Gavia Lake (Aug. 21, 1952) there were six jaegers in one group.
Stercorarius longicaudus Vieillot: Long-tailed jaeger.—Specimens, 5: Kaolak River, 159°47'40", 70°11'15", 30 ft., 1, No. 30738, ad. female, July 12, 1951; Kaolak, 160°14'51", 69°56'00", 178 ft., 4, Nos. 30734-30737 including 2 ad. males and 2 ad. females, July 21, 1951.
The long-tailed jaeger was the second most abundant of the three jaegers at Topagaruk (July 5-10, 1951). The greatest number seen on any one day was three. At Kaolak River (July 12-19, 1951) this species was the most common jaeger. On a four hour field trip (July 15 and 18) we saw six birds. When in groups of three or more, they frequently chased each other and called vigorously. One adult female shot on July 12, weighed 300 grams. The largest ovum in the female was 1.2 mm in diameter and the ovaries were 5 and 6 mm long.
Within 1⁄5 of a mile of our camp at Kaolak (July 21-27, 1951) there were three breeding pairs of jaegers. On a four hour trip beyond this limit we saw as many as 14 individuals. Most of these were in groups of three and were commonly seen flying over meadows and along ridges. Single birds hunted by hovering or swinging upward. Territories vacated by our collecting adult birds were not immediately filled by other nesting jaegers. One pair of jaegers nested in a broad grassy meadow. The female was aggressive and demonstrative and called continually above her young. The male was less demonstrative but joined the female when she began calling. On July 24, four jaegers flew over areas where brown lemmings had been trapped in greatest numbers. Two adult males shot on July 21, weighed 270 and 250 grams. The testes of these two birds were 5.5 and 8.0 mm long. Two adult females from the same area, and shot on the same date as the males, were larger than the males. The females weighed 285 and 298 grams.
At Barrier Lake (July 29, 1951) we observed three long-tailed jaegers, all chasing and harassing a glaucous gull. These jaegers hunted mostly along ridges and over marsh. At midnight these birds were still hunting and flying about. Other long-tailed jaegers were on the lake from July 29 to August 4 inclusive.
At Gavia Lake (Aug. 21-23, 1952) two long-tailed jaegers fed from our refuse pile only 30 feet from our tent. A single individual was noted at Lake Peters on July 25, 1952, and one at Driftwood on August 27, 1952.
Larus hyperboreus barrovianus Ridgway: Glaucous gull.—Specimen, 1: Topagaruk, 155°48', 70°34', 10 ft., No. 30739, ad. male, July 9, 1951.
Robert McKinley told us that on May 16, 1952, approximately 25 gulls, probably glaucous gulls, arrived at the Arctic Research Laboratory and remained until May 25. On July 4, 1951, there, we recorded all gulls passing over the ice from 8:45 A.M. to 9:45 A.M. At this time the shore line and first 100 feet of water was free of ice; beyond, seaward, the ice was rough and dark for ¼ mile, succeeded by white ice for ¼ mile, next the high pressure ridge, and then open water of the Arctic Ocean. Glaucous gulls, singly, passed to the southwest and to the northeast at intervals of 6(3-10) minutes at a distance of 500(300-800) feet from the shore line, except for one bird that was approximately one mile off-shore.
On July 10, 1952, off-shore from the Laboratory, where garbage from camp was deposited on the ice, approximately 130 glaucous gulls were present—some resting on the ice and some flying. At six P.M., four hours later, 84 gulls including several immatures remained. Birds in groups were constantly walking about or flying short distances, but lone individuals stood perfectly still for long periods. On July 11, only 22 birds remained; they were flying up and down the shore line. At Topagaruk (July 5-10) glaucous gulls fed on the refuse pile at camp. The number varied from day to day, from as few as 10 to as many as 22; a few remained at the feeding grounds at all times.
The testes of an adult male (30739), shot on July 9, 1951, at Topagaruk were 15 mm long and 9 mm thick.