The young female differs from the adult female in having a smaller and weaker bill and softer plumage; the black breast patch is entirely lacking; the breast, sides, and flanks are barred with dusky, but less distinctly than in the adult; and the yellow of the central breast and abdomen is much paler. These two juvenal plumages are worn for only a short time in summer. I have seen young males molting into their first winter plumage, which is practically adult, as early as August 9; and young females begin to show the increasing black breast patch as early as August 6; but this molt is slow, or variable, and is sometimes not completed until November or December. Adults apparently have their complete annual molt mainly in August and September. _Food._--Mrs. Florence M. Bailey (1928) says: “In 17 stomachs examined, 87 percent was animal matter and 13 percent vegetable. Of the animal contents, 86 percent was ants, and cambium made up 12.55 percent of the total food.” Grinnell and Storer (1924) write: In the Yosemite region the Williamson Sapsucker is closely associated with the lodgepole pine. While this tree seems to furnish the bird’s preferred source of forage, practically all other species of trees within its local range are also utilized. We saw workings attributable to this sapsucker on the alpine hemlock, red and white firs, Jeffrey pine, and quaking aspen. The amount of work which this sapsucker will do upon a single tree was impressed upon us while we were at Porcupine Flat in early July, 1915. In that locality there was a lodgepole pine (_Pinus murrayana_) about 60 feet high, which showed no marks of sapsucker work previous to the current year. The tree was in full leafy vigor and measured 8 feet 3¼ inches in girth at 3 feet above the ground. There were numerous live branches down to within 6 feet of the ground. Twenty-six irregularly horizontal rows of fresh punctures were counted on one side of the trunk, the lowest being only 18½ inches above the ground, and the highest about 40 feet. * * *