Although the Arctic three-toed woodpecker usually nests at no great height above ground, there are a few exceptions to this rule, mainly in the western portion of its range. Grinnell and Storer (1924) record a nest seen in the Yosemite region that was 50 feet above ground in a dead lodgepole pine. Harry S. Swarth (1924) found, in the Skeena River region, the highest nest of which I can find any record; he says: “A nest of the Arctic three-toed woodpecker was found in Kispiox Valley. It was placed in a dead and charred Engelmann spruce, in a strip of spruce woods bordering a muskeg otherwise surrounded by poplar forest. The nest hole was eighty feet from the ground. It was two and one-half inches in diameter and one foot deep, drilled through an outer sheath of sound, hard wood, and downward through soft, rotten ‘punk.’” _Eggs._--The number of eggs laid by the Arctic three-toed woodpecker varies from two to six, four being the commonest number. These vary from ovate to elliptical-ovate, the former shape prevailing. The shell is dull or only slightly glossy and is pure white. The measurements of 39 eggs average 21.32 by 18.94 millimeters; the eggs showing the four extremes measure =25.9= by 18.7, 25.1 by =20.2=, and =22.35= by =17.53= millimeters. _Young._--The period of incubation is about 14 days; both sexes assist in this and in the care of the young. Only one brood is raised in a season, but if the eggs are taken, a second set will be laid, often in the same nest. Mr. Achilles (1906) watched a nest containing young for 24 consecutive hours, he and a companion taking turns at the vigil and sleeping alternately within ten yards of the tree; he writes: The parents, when feeding their young, usually alighted within a space of three feet below the hole, and never directly at its entrance. They would pause here for a moment as though fearing they were observed by someone. Then they would hop up to the hole and look in, anywhere from two up to six times, as if accustoming their eyes to the darkness. Once in a while grubs could be seen in their bills, but, from the actions of the birds when feeding their young, they appeared to be regurgitating. During twenty-four hours the female fed the young thirty times, and the male twenty-nine times.