WILLOW WOODPECKER
HABITS
The downy woodpeckers of California were for many years all called D. p. gairdneri, until Dr. Walter K. Fisher (1902) called attention to the smaller and lighter-colored race, which inhabits much of the coast region and nearly all the lowlands of southern California. For this race, he very properly revived Malherbe’s name, as given above, for this name was based on birds taken near Monterey. He gives as the characters of the willow woodpecker:
Smaller than Dryobates pubescens gairdneri, with smaller feet; under parts lighter; the elongated superciliary patch and rictal stripe extending over sides of neck, pure white, instead of smoky white of gairdneri; tertials always more or less spotted with white. * * *
Dryobates pubescens turati is a southern representative of gairdneri, which it resembles in the smoky under parts and restricted areas of white on the wings, and from which it differs in its smaller size, much smaller feet, and clearer white markings of head. The present form is near true pubescens of the Southern States, but differs from it in having much less white on the wings, the coverts and tertials of pubescens being conspicuously and often heavily marked with white. * * *
The willow woodpecker in a typical form breeds from Los Angeles and San Bernardino counties north in the coast ranges to San Francisco Bay, and along the west slope of the Sierra Nevada at least to Yuba County. Intergradation with gairdneri occurs over the coast region north of San Francisco Bay and in the mountains at the head of the Sacramento Valley.
Grinnell, Dixon, and Linsdale (1930) say of the haunts of the willow woodpecker in the Lassen Peak region: “Downy woodpeckers were seen most often close to streams and in orchards. Their forage places included the limbs or small trunks of willow, alder, cottonwood, sycamore, valley oak, blue oak, digger pine, and yellow pine trees.”
Nesting.—Major Bendire (1895) writes: “Mr. Charles A. Allen informs me that it breeds in the oaks and willows along the Sacramento River, Calif., but that it is not common. Its breeding sites seem to be confined to deciduous trees, preferably dead ones, or old stumps, and besides those already mentioned, sycamore and cottonwoods are occasionally used. Their nesting sites are rarely found at any great distance from the ground, usually ranging from 4 to 20 feet up and rarely higher.”
W. L. Dawson (1923) says: “Willow woodpeckers, in the wild, place their nests at considerable heights in deciduous trees, and those, if possible, among thick growths on moist ground. Both sexes assist in excavation, as in incubation. Partially decayed wood is selected, and an opening made about an inch and a quarter in diameter. After driving straight in for an inch or two, the passage turns down and widens two or three diameters. At the depth of a foot or so the crystal white eggs are deposited on a neat bed of fine chips. Incubation lasts twelve days, and the young are hatched some time in May.”
Eggs.—The willow woodpecker lays three to six eggs, more commonly four or five; it may occasionally lay seven, as some of the other western races have been known to do. The eggs are typical of the species. The measurements of 40 eggs average 18.74 by 15.20 millimeters; the eggs showing the four extremes measure 22.3 by 15.7, 18.4 by 16.3, 17.3 by 14.5, and 18.0 by 14.4 millimeters.
Food.—Mr. Dawson (1923) writes:
It is as an orchardist that the Willow Woodpecker deserves the most careful consideration. Bird-lovers are, perhaps prone to superlatives in commending their friends, but it is safe to say that a more useful bird for his ounces than the downy woodpecker does not exist. He eats not only ants and the larvae of wood-boring beetles, but scale insects, plant lice, and the pupae of the detestable coddling moth. The evidence is clear that these incomparable tree experts, together with their friends, the nuthatches, the chickadees, and the creepers, would insure the health of our orchards if they were numerous enough. It becomes of the highest importance, then, to study their welfare in turn. In the northern and more elevated valleys of the State, it may be worth while to offer them nuts or to hang out a bit of suet in winter. In the South no such precautions are necessary. A fundamental consideration, however, is the provision of suitable nesting sites. Experiment has shown that the downy’s forage range during the breeding season is not extensive. The clamoring young are fed by the product of nearby trees (fed, it may be, a thousand insects a day). Their services, therefore, must be secured in the orchard; and to this end the orchardist must consent to leave certain dead branches—a foot or so at the base of the larger ones will do—for a nesting site. Dead wood, of course, invites insects; but the most serious and frequent mistake which our California orchardists make is to trim out all the dead wood from the fruit trees. A pair of Willow Woodpeckers, or of Slender-billed Nuthatches, will clean out all the dangerous pests from a dead tree, and sixteen live ones to boot.
Grinnell and Storer (1924) made some studies of the feeding habits of the willow woodpecker in the Yosemite region, of which they say:
A pair of Willow Woodpeckers proved to be regular tenants of Curry’s apple orchard on the floor of the Yosemite Valley. They, or their ancestors, had evidently worked there for some years, with the result that most of the 150 trees in the orchard showed marks of their attention, and many of the trunks were fairly riddled with drillings somewhat like those of the sapsucker. * * *
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.
We had always supposed that the rapid series of notes uttered by this species were given only by the adult male and hence constituted a sort of song. But on June 24, 1920, in Yosemite Valley a juvenile male was found, with his head out of a nest hole eight feet above the ground in a dead branch of a live willow, giving every few moments this very series of notes. The large crown patch of red on this bird established its age and sex clearly. There was every indication that the notes were being given as a food call.
M. P. Skinner contributes the following note:
One seen in Sequoia National Park in August was drilling at the bases of willow shoots near a river. It perched lengthwise of the stems. It managed to keep well hidden, but worked industriously and did not change its position much during the short time that I could see it. Later, I caught a glimpse occasionally of the woodpecker’s red head, although the bird kept hidden most of the time. This reminded me that I had often wondered why red usually marked a woodpecker’s head. Certainly it makes a wonderful recognition mark. In that way it might well be that red on the constantly moving head of the woodpecker would be of value to the race.