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.