Weights of 10 males and 10 females, shot in the period July 14-August 29, 1951, at several localities on the Arctic Slope were: male 20(17-24), female 18(16-20) grams. In an adult male, shot on July 22 at Kaolak, the testes were two mm long but in other males, shot in the period July 14-August 29, the testes averaged 1.2 mm. The ovaries of adult females for this same period also had receded to normal non-breeding size. Juveniles on July 13 at Porcupine Lake averaged 20 grams in weight; the shortest was 125 mm in total length and the largest 140 mm. Adults in this same period averaged 144 mm in total length. Two adult males collected on July 22 and 24, 1951, at Kaolak, were molting.
Spizella arborea ochracea Brewster: Tree sparrow.—Specimens, 10: Gavia Lake, N White Hills, 150°00', 69°35', 460 ft., 1, No. 31340, juv. male, August 22, 1952; 9⁄10 mi. N and 9⁄10 mi. W Umiat, 152°10'58", 69°22'53", 380 ft., 1, No. 31347, ad. female, July 1, 1952; Umiat, 152°09'30", 69°22'08", 352 ft., 1, No. 31341, ad. male, June 26, 1952; Wahoo Lake, 146°58', 69°08', 2350 ft., Nos. 31342-31343, ad. males, July 6, 8, 1952; Driftwood, Utukok River, 161°12'10", 68°53'47", 1200 ft., 2 (skins) Nos. 31345, ad. male, August 29, 1952, and 31346, ad. female, August 28, 1952, and 1, No. 31344, ad. male, August 28, 1952; Chandler Lake, 152°45', 68°12', 2900 ft., 2, Nos. 30783, juv. male, 30784, a juv. of unknown sex, August 19, 1951.
Four adult males shot in the period July 1-15, at Umiat, Wahoo and Porcupine lakes averaged 158(155-165) mm in total length and 18(16-18) grams in weight whereas 12 adult males (Aug. 14-31) from Chandler Lake, Umiat, Gavia Lake and Driftwood averaged 161(156-165) mm in length and 19(16-21) grams in weight. A male (June 26) from Umiat was 160 mm long, weighed 15 grams, and had testes 4 mm long. Males from Wahoo Lake (July 6 and 8) had testes 9 and 5 mm long. Males (August 19) from Chandler Lake were molting on the entire body.
On June 24, 1952, at Umiat, we examined three nests. One of the three contained incubated eggs; skeletal elements were present in the embryos. This nest, 150 mm in diameter and 52 mm in depth, was on the side of a mound three feet high covered with grass. The cup was 55 mm in diameter. The lining, 14 mm thick, was ptarmigan feathers averaging one inch long mixed with successive layers of stems of fine grass. The cup weighed four grams and rested directly on the ground. The outer part of the nest was coarse stems of a grass and was 30 mm thick. The edge and upper side, away from the mound, had a 40-millimeter thickness of mosses and lichens that may have served primarily as camouflage rather than as insulation. The nest, minus the lining weighed nine grams. The second nest held four eggs containing embryos. The top was flush with the surface of the ground on a slightly elevated bench on a hillside supporting Ledum, Vaccinium, Alnus, mosses and lichens. The greatest width of the nest was 120 mm; the lining, 11-millimeters thick, was of ptarmigan feathers succeeded by 13 mm of alternating layers of new dry grass stems and ptarmigan feathers. The down-slope side of the nest was protected by 29 mm of sphagnum, old grass stems and other dry plant material. The third nest of four eggs was among grasses at the base of a willow. The new leaves on this willow were just visible and the catkins had attained full growth.
The earliest date that juvenal tree sparrows were noted in the field was on July 10, 1952, at Wahoo Lake. One juvenile shot on this date was 85 mm long and could not fly. The parent bird was still attending the young bird.
Tree sparrows on the Arctic Slope usually live among high dwarf willows at the mouths of canyons. At Porcupine Lake (July 13-18, 1952) however, they inhabited marshes of sedges, grasses and hummocks of cotton-grass. At night they roosted in depressions in the ground or between hummocks of sedges, where, without overhead protections they endured temperatures of as low as 34 degrees Fahrenheit.
In one mile of a glaciated canyon southwest of the south end of Chandler Lake (Aug. 19, 1951) tree sparrows were the commonest species but there were few birds of any kind there. This canyon extended in an east-west direction and was bordered by high mountains, the sun being excluded in early morning and late afternoon. In the valley of Chandler Lake, on the same day, the tree sparrows were numerous especially among willows on the side of the valley. On this date there was an abrupt increase in numbers of tree sparrows; the number of Lapland longspurs and wheatears was less than a week before. On August 22, we did not see tree sparrows at Chandler Lake whereas three days earlier there were hundreds in the area. On August 23 only 15 were noted and these were in willows. On August 25, only a single bird was noted.
At Umiat (Aug. 30, 1951) a few tree sparrows were present. In this area (Sept. 1) the birches were turning a brilliant red, even more brilliant than on the previous day. The large alders were nearly all yellow. The season was not so far advanced here, however, as at Chandler Lake on August 25. At Driftwood tree sparrows were noted from August 27 to 31 inclusive. On August 28 a flock of 12 was observed.
Zonotrichia leucophrys gambelii (Nuttall): White-crowned sparrow.—Specimens, 3: Mount Mary, S Lake Peters, 145°10'02", 68°20'30", 2920 ft., 1, No. 31348, juv. female, August 3, 1952; Driftwood, Utukok, 161°12'10", 68°53'47", 1200 ft., 1 (skin) No. 31349, ad. male, August 29, 1952; Chandler Lake, 152°45', 68°12', 2900 ft., 1, No. 30786, an ad. of unknown sex, August 19, 1951.
On the north side of the valley at Umiat, the white-crowned sparrows were calling (June 27, 1952) throughout the day. At Wahoo Lake (July 3-11, 1952) singing birds were frequently heard on south-facing slopes of the valley. At Lake Peters (Aug. 3, 1952) one bird was at the base of a moraine some distance from willows or high vegetation. Only two birds were seen at Chandler Lake (Aug. 19 and 25, 1952); they were feeding in a dense growth of willows. The juvenal female shot on August 3, 1952, at Mount Mary was 180 mm long and weighed 26 grams.