Rex Brasher (1926) writes:
Seated under a cluster of small maples, one day in early May, I watched the interesting courting antics of the pair. The jaunty male’s favorite position was one in which he appeared to be almost standing on his tail. With bill upright, wings thrown forward, and tail wide-spread he repeated over and over what was undoubtedly intended for a love-song, a series of notes divided between chuckles and whistles. But the strangest, most mystifying performance was a series of backward drops on the under side of a limb inclined about forty-five degrees. * * * Why didn’t the little acrobat fall when he released his claws? Studying his movements carefully through the binoculars, I came to the conclusion that at the instant of releasing his grip he jerked his body toward the limb with sufficient impetus to catch the bark six inches or so below.
Lewis O. Shelley says in his notes: “I have watched the act of copulation of the hairy woodpecker and noted its dissimilarity to the downy. For the hairy invariably instills a follow-up procedure to the display, the male coming to her call and, soon thereafter, hopping up the branch toward her with a short jerking movement, in which he calls wick-up, wick-up, wick-up, wings agitating, this immediately followed by copulation.”
Nesting.—The hairy woodpecker is rather rare, as a breeding bird, in my home territory in southeastern Massachusetts, but I have the records of 12 local nests. It shows a decided preference for deciduous woodlands, six of the nests being in dry, upland woods and two in maple swamps; of the other four nests, three were in apple orchards, close to extensive woodlots, and the fourth was in a small, living, red maple in a swampy meadow, some distance from any woods. The birds showed no decided preference for any one species of tree; three nests each were found in maples and apple trees, two each in chestnuts and poplars, and one each in a dead oak and a dead beech. Only four nests were in dead trees or dead branches; the others were all in living hardwoods. The heights from the ground varied from 5 feet in a dead poplar stub to 30 feet, or more, in tall chestnuts or maples. The entrance to the nesting cavity often appears nearly, or quite, circular, but on careful measurement will usually be shown to be more or less elliptical, higher than broad; a typical entrance hole that I measured was 1⅞ high by 1½ inches wide. The depth of the cavity was found to vary from 10 to 12 inches, but Mr. Shelley (1933) measured one that was 15 inches deep, and even deeper holes have been reported. Owen Durfee’s notes give some very careful measurements of two of our local nests, one of which is worth quoting as showing an unusually elliptical entrance: “The entrance to the nest was on the northeast side of the trunk of a live chestnut and 22½ feet from the ground. The tree leaned toward the east about 2 feet. At the butt it was 9 inches in diameter and at the opening about 6½ inches. The opening had the usual elongated appearance, 2⅝ high by 1⅞ inches wide. The top of the hole went straight in across the cavity for 4½ inches, the bottom edge of the opening slanting up ¾ of an inch while going in 1½ inches. Then the cavity went nearly straight down below the hole for 12 inches, enlarging only a trifle, so that the base was about 4½ inches in diameter. The shell of the tree was only about ⅞ inch thick on one side but on the other was 2 inches thick.”
Dr. Sutton (1928b) says of the nests in Pymatuning Swamp, Pa.: “The cavities were drilled near the tops of dead trees which nearly always stood in water. It was impossible to climb many of them because their bases were weak; but the clamoring of the young birds could be heard some distance away. On May 30, 1922, I located six nests within a half hour by watching the parent birds and listening for the young. * * * The twenty-six nests averaged roughly over thirty feet from the ground.”
T. E. McMullen mentions in his notes a Pennsylvania nest that was 50 feet from the ground in a large maple in some woods. J. Claire Wood (1905) reports some very high nests in Michigan; one was in the “trunk of very large barkless dead elm about 50 feet above ground”; another was in the trunk of a “dead beech 55 feet up and just under a large limb.”
The female probably selects the nesting site, but both sexes work alternately at the labor of excavating the cavity. This work requires one to three weeks, depending on how hard the wood is; a cavity in the soft wood of a poplar, which is a favorite with this species in some localities, might be excavated in a very short time, but I have known a pair to take over three weeks to excavate a nest in a hard maple; the trunk of a living tree may have a soft center, and some of the birds seem to be clever enough to select such a tree. A new nest may often be recognized by the presence of fresh chips on the ground around the tree, as the birds are not very particular about removing them.
The male sometimes digs out another shallower hole near the nesting tree, which he uses as a sleeping place. Usually a fresh hole is made each season, but I have seen occupied holes that were very much weathered, as if they had been occupied for more than one season; in such cases, the cavity may be deepened somewhat and the bottom covered with fresh chips. I once found a pair of these woodpeckers excavating their domicile, which they later abandoned, as I found on a later visit that the hole was partly full of water and sap. They are not always successful in their first attempt, for this and other reasons, and may have to start two or three holes before they find just the conditions they want. The eggs are laid on a soft bed of fresh chips at the bottom of the cavity and are usually half buried in it; no nesting material is carried in.
Eggs.—The hairy woodpecker lays three to six eggs, but four seems to be the commonest number. The eggs vary in shape from oval to elliptical-oval, usually more nearly oval. The shell is smooth and often quite glossy. The color is pure white, but in fresh eggs the yolk shows through the translucent shell, giving the egg a beautiful orange-pink color. The measurements of 47 eggs average 23.81 by 18.04 millimeters; the eggs showing the four extremes measure 29.50 by 18.80, 28.70 by 18.90, and 20.57 by 16.26 millimeters.
Young.—Only one brood is raised in a season, but, if the nest is robbed, the female will lay a second set after an interval of 12 or 14 days, and sometimes even a third set; often subsequent layings may be in the same nest hole.