At Chandler Lake, the decrease in numbers of Lapland longspurs was synchronized with autumnal changes in weather. On August 15, 1951, the longspurs were numerous; 40 or 50 individuals were seen in the course of an hour's walk. On August 19 there was a noticeable decrease in numbers of individuals and by August 22, only three were seen. In this period of decreasing numbers, they were more numerous and active in the morning than in the evening or in inclement weather. The behavior pattern of leaving the ground with an audible commotion and flapping of wings on the vegetation also was characteristic of this period of decreasing numbers of the longspur population. At 1/2 mile south of the Arctic Research Laboratory (Sept. 7, 1952) only a single longspur was noted. The short-eared owl and especially the pigeon hawk consistently preyed on longspurs. Only one longspur (an adult female No. 30854) in 75 specimens examined had the bone of the skull damaged by parasites. Adult males are larger than adult females (July). In the breeding season adult females average 3 grams lighter than males. In the latter part of summer, however, females "catch up" in weight with the males. As early as the middle of July, juveniles are nearly as large as adults in cranial measurements. The increase in weight in juveniles was from 21.5(18-25) in ten juvenal males shot in the period July 12-16, at Kaolak River to 25.2(22-27) grams in nine juvenal males shot in the period July 29-August 2 at Teshekpuk Lake. The testes of adults gradually decrease in size from July to August; their average length was 7.7(4.0-12.0) mm in nine adult males shot in the period July 6-10 at Topagaruk but only 2.2(1.5-3.0) in six adult males shot in the period July 12-26, at Kaolak and Kaolak River. By August 1, at Teshekpuk Lake the testes of nine adult males averaged 1.4(1.0-1.5) in total length, which is only slightly larger than the average size of the testes 1.2(1.0-2.0) of nine juveniles shot in the period July 29-Aug. 2, at Teshekpuk Lake. +Calcarius pictus+ (Swainson): Smith's longspur.--Specimens, 2: Wahoo Lake, 146 deg.58', 69 deg.08', 2350 ft., No. 31353, ad. male, July 9 and No. 31354, ad. female, July 7, 1952.