Of the spring drumming, perhaps a part of courtship, Dr. Harry C. Oberholser (1896b) says:
In spring the drumming of the yellow-bellied sapsucker may usually be easily recognized by the following peculiarities. Four or five taps given in quick succession are followed by a short pause, this being soon succeeded by two short quick taps; then another pause, and two more taps in somewhat less rapid succession than the first; followed by yet another pause, and two additional taps still a little slower. This is sometimes slightly varied with regard to the number of taps; and occasionally also the latter part consists only of single quick taps with an increasing interval toward the last.
The difference between the tapping of the sapsucker and of the hairy and the downy woodpecker is described in the life history of the latter bird. Wendell Taber told Mr. Bent that he succeeded in calling up three of these birds by imitating their drumming with a fountain pen on a dead tree; one of them alighted on the tree on which he was drumming.
Nesting.—William Brewster (1876a), writing of the nesting of the sapsucker at Umbagog Lake, Maine, says:
They arrive from the South, where they spend the winter, from the middle to the last of April, and, pairing being soon effected, commence at once the excavation of their nests. The trees usually selected are large dead birches, and a decided preference is manifested for the vicinity of water, though some nests occur on high ground in the interior of the woods, but never so abundantly there as along the margin of rivers and lakes. Both sexes work alternately, relieving each other at frequent intervals, the bird not employed usually clinging near the hole and encouraging its toiling mate, by an occasional low cry. With the deepening of the hole arises the necessity for increased labor, as the rapidly accumulating debris must be removed, and the bird now appears at frequent intervals at the entrance, and, dropping its mouthful of chips, returns to its work. A week or more is occupied in the completion of the nest, the time varying considerably with the relative hardness of the wood. A small quantity of the finer chips are left at the bottom to serve as a bed for the eggs. * * * The labor of incubation, like all other duties, is shared equally by the two sexes. * * *
All nests examined upon this occasion [an occasion when he found half a dozen nests] were of uniform gourd-like shape, with the sides very smoothly and evenly chiselled. They averaged about fourteen inches in depth by five in diameter at the widest point, while the diameter of the exterior hole varied from 1.25 to 1.60 inches. So small, indeed, was this entrance in proportion to the size of the bird, that in many cases they were obliged to struggle violently for several seconds in either going out or in. The nests in most instances were very easily discovered, as the bird was almost always in the immediate vicinity, and if the tree was approached would fly to the hole and utter a few low calls, which would bring out its sitting mate, when both would pass to and from the spot, emitting notes of anxiety and alarm. The bird not employed in incubation has also a peculiar habit of clinging to the trunk just below the hole, in a perfectly motionless and strikingly pensive attitude, apparently looking in, though from the conformation of the interior it would be impossible for it to see its mate or eggs. In this position it will remain without moving for many minutes at a time.
Henry Mousley (1916) states that the bird “often nests year after year in the same tree (but not necessarily in the same hole) the favourite ones here [Hatley, Quebec] being elm, poplar, and butternut. * * * Of two nests examined the average dimensions are as follows, viz.: entrance hole 1⅜ inches in diameter, extreme depth 10¾ inches, and width 2⅞ inches.”
Philipp and Bowdish (1917) say of the nesting site in New Brunswick: “The favorite situation was the dead heart of a live poplar, most often on the bank of a stream, and facing same, but some nests were in totally dead trees, of different kinds. They ranged from eight to forty feet from ground.”
Bendire (1895) says that the birds “are devoted parents, and when incubation is somewhat advanced, or the young have been recently hatched, the bird on the nest is loath to leave it, and will sometimes allow itself to be captured rather than to desert its treasures.”
Eggs.—[Author’s note: The yellow-bellied sapsucker lays four to seven eggs to a set, though five or six eggs are more commonly found. They vary from ovate to elliptical-ovate and sometimes to elliptical-oval. The shell is smooth and either dull or moderately glossy. They are pure white, like all woodpeckers’ eggs. The measurements of 52 eggs average 22.44 by 16.92 millimeters; the eggs showing the four extremes measure 24.9 by 17.0, 23.8 by 18.0, 20.57 by 16.26, and 22.1 by 15.5 millimeters.]