The cause of this strongly contrasted sexual coloration unique among the woodpeckers of the United States is one of the unsolved problems of ornithology that stimulates speculation and so adds zest to the study. Is it, as Mr. Swarth suggests, that the female is still in a primitive stage of development? Correlating the brown coloration of the pasture-frequenting flickers with the ant-eating habits so marked in the Rocky Mountain sapsucker, it would seem that the color of the female might have been ancestrally adapted to a more open habitat than that in which the pair are found today; or has the ant-eating habit been diverted from ants that live on the ground in the open to those that live on tree trunks? The feeding habits of the anomalous pair should be carefully studied in the field. Dr. Edgar A. Mearns (1890b) says that in Arizona it “breeds very commonly at the highest altitudes, frequenting the spruce and fir woods. It seldom descends far into the pine belt during the breeding season, although it is found in the pines in winter, occasionally descending even to the cedars in severe weather; and after the nesting season it frequently roves down to the pine woods with its young. When shot, it usually fastened its claws into the balsam bark and remained hanging there after life was extinct.” Milton P. Skinner says in his Yellowstone Park notes: “In this Park, the Williamson sapsucker lives below 7,000 feet and prefers mixed forests of aspen and fir, but it is not particular whether in dense forest or in the borderland between forest and open.” _Spring._--Mr. Swarth (1904) witnessed a well-marked spring migration in the Huachuca Mountains, Ariz., of which he says: On April 6, 1902, I saw about a dozen Williamson Sapsuckers near the summit of the mountains at an altitude of about 9,000 feet. Though not at all in a compact flock they seemed to keep rather close together, and when one flew any distance away, the others soon followed. The bulk of them were females, and but one or two males were seen, one of which was, with great difficulty secured, for they were very wild. On April 9 several more were seen and a female secured at this same place; and a male was taken a mile or two from this place, at an altitude of nearly 10,000 feet. These were the last I saw in the spring, though they do occur later as I have a female that was taken in the Huachucas by H. Kimball on April 20, 1895.