However destructive this drilling may seem to be, it does not seriously affect the vitality of the trees; the pits are but 4 to 5 mm. deep, penetrating only those outer layers of the bark which after a time scale off. We should judge that all evidence of this woodpecker’s work is thus removed through natural process within about three years. The heartwood of the tree therefore seems not to be damaged at all by the woodpecker’s work; it _is_ damaged, however, by the work of the true sapsucker. Our inference from these facts is that the willow woodpecker feeds on the inner layers of bark, which the bird exposes through the perforations described above. We watched a bird at work; moreover, bits of inner bark-fibers were found adhering to the bristles around the bill of a bird shot. Evidently this observation and report started the same old controversy that arose in connection with the eastern bird, which has been referred to under that subspecies. Charles W. Michael intimated, in course of conversation with Dr. Grinnell, that they were mistaken in ascribing these drillings to willow woodpeckers rather than to red-breasted sapsuckers. This led to the publication, by Dr. Grinnell (1928a), of the evidence produced by Mr. Michael and himself, to which the reader is referred. In spite of some evidence, and more supposed evidence, to the contrary, it now seems to be generally conceded that the downy woodpeckers seldom, if ever, drill these holes for themselves, but that they often feed from holes drilled by sapsuckers. The small amount of drilling done by the downy woodpeckers seems to do the trees no great harm. _Behavior._--Grinnell and Storer (1924) write: The quietness of the willow woodpecker, as compared with most other species in its family, is noteworthy. We heard no single call note from it, and only at long intervals did we hear the indescribable short trill characteristic of this bird. Individuals are much restricted in range, foraging along a relatively short line of cottonwoods or willows day after day. Once a bird is located, it can usually be found in the same place regularly. When foraging it moves about with very little commotion, and even when drilling for insects works so quietly that only a keen auditor can detect its presence. No matter what the season of the year, a pair of these birds is to be found usually within hearing of each other. The bird’s close adherence to deciduous trees makes it more conspicuous and easier to observe in late fall and winter than in the summertime when the trees are fully leaved out; but even in winter, our experience with the willow woodpecker led us to consider it about the most elusive of all the diurnal birds of the Yosemite region.