WILLIAMSON'S SAPSUCKER 159 



white, instead of scarlet ; the center of the breast and abdomen is dull 

 yellowish white, instead of bright "lemon-chrome"; the sides and 

 flanks are barred, instead of striped or spotted, with dusky. 



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 sum- 

 mer. 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 ex- 

 amined, 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 (Finns miirrayana) 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 3^/4 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 18% inches above the ground, 

 and the highest about 40 feet. * * * 



During the winter months when sap is practically at a standstill in the 

 coniferous trees at high altitudes, the Williamson Sapsucker must needs seek 

 other fare. A few of our own observations added to those of other naturalists 

 suggest that during the winter season the birds may forage in a large part on 

 dormant insects or on Insect larvae hidden in crevices in the bark. If such is the 

 case, whatever the damage done by these birds to the forest as a whole 

 during the summer months, it is partially offset by their wintertime activity. 

 In any event, the attacks of the Williamson Sapsucker on the lodgepole pines 

 of the central Sierra Nevada cannot be considered as of great economic im- 

 portance, for these trees are there used little if at all for lumber or for any 

 other commercial purpose. 



Behavior.— Dv. J. C. Merrill (1888), at Fort Klamath, Oreg., found 

 this sapsucker "shy and very suspicious. A noticeable habit here is 



