Eggs.—The red-breasted sapsucker lays usually four or five eggs, sometimes as many as six. Like all woodpeckers’ eggs, they are pure white, usually with very little or no gloss, and they vary from ovate to rounded-ovate. The measurements of 13 eggs average 23.79 by 17.25 millimeters; the eggs showing the four extremes measure 24.6 by 17.0, 23.81 by 17.86, 22.5 by 17.5, and 24.5 by 16.6 millimeters.
Young.—Incubation is said to last about 14 days; this duty and the care of the young is shared by both parents. Mrs. Irene G. Wheelock (1904) says of a nest that she watched: “Incubation began May 30, and lasted fifteen days. The young were fed by regurgitation for the first two weeks. * * *
“The young sapsuckers left the nest on the seventh of July, and clung to the nest tree for three days. Here they were initiated by both parents into the mysteries of sap-sucking. A hole having been bored in front of each, with grotesque earnestness the mother watched the attempt to drink the sweet syrup. During this time both insects and berries were brought to them by the adults, in one hour one youngster devouring twelve insects that looked like dragonflies.”
Mrs. Florence M. Bailey (1902) writes:
The last week in July at Donner Lake we found a family of dull colored young going about with their mother, a handsome old bird with dark red head and breast. They flew around in a poplar grove for a while, and then gathered in a clump of willows, where four young clung to the branches and devoted themselves to eating sap. The old bird flew about among them and seemingly cut and scraped off the bark for them, at the same time apparently trying to teach them to eat the sap for themselves; for though she would feed them at other times she refused to feed them there, and apparently watched carefully to see if they knew enough to drink the sap. When the meal was finally over and the birds had flown, we examined the branch and found that lengthwise strips of bark had been cut off, leaving narrow strips like fiddle-strings between. At the freshly cut places the sap exuded as sweet as sugar, ready for the birds to suck.
Plumages.—Like other young sapsuckers, the young of this species are hatched naked, but the juvenal plumage is acquired before they leave the nest. In the juvenal plumage, in which the sexes are alike, the wings and tail are essentially as in the adult; the head and neck, except for the white stripe below the eye, are dark grayish sooty, though the forehead and crown are usually more or less tinged with dull red; the sides and flanks are more or less barred with dull gray and white; and the abdomen is dull yellowish white.
By the last of July, or first of August, the molt into the first winter plumage begins, with an increasing amount of red coming in on the crown, throat, and breast; at the same time the yellow of the abdomen becomes brighter. This molt continues through fall and is often not complete until November or later. The young bird is now much like the adult. In fall birds, both adult and young, the red of the head and breast, is much duller than in spring, “Brazil red” to “dragon’s blood red” in the fall, and “scarlet red” or bright “scarlet” in the late winter and spring; this is due, of course, to the wearing away of the tips of the feathers; in early summer, just before molting, the red is decidedly brilliant.
Adults have a complete annual molt, beginning sometimes in July and lasting through August or later.
Food.—The food of the red-breasted sapsucker is much like that of its close relatives in the varius group. M. P. Skinner writes to me: “I have found red-breasted sapsuckers drilling on cottonwoods, willows, yellow pines, and lodgepole pines; but all the actual feeding I have seen was on willows. Mr. Michael tells me that these birds work largely on the apple trees that have been planted in various parts of the Yosemite Valley. When a sapsucker is at its wells, it takes a sip now and then, but considerable time is used in watchful guarding, or in driving away intruders or would-be robbers. In the case of such wells as I found on willow stems, I could see no established regularity in arrangement. They looked as if the bark had been irregularly scaled off. In fact, such work may be necessary to secure the inner bark; yet the birds actually took sap at such wells. One had a dozen willow stems on which it drilled and sipped in succession; each one was only a few inches from the next; and the bark of each, both above and below the wells, was worn smooth. This bird went from well to well in regular order, then back to the first well to begin again. Although sap formed the bulk of their food in August, I have seen them also searching the bark for insects during that same month.”
McAtee (1911) lists the following trees that are attacked by the red-breasted sapsucker: Cottonwoods, willows, walnuts, birches, oaks, barberry, sycamore, mountain-ash, pears, apples, peaches, plums, apricot, orange, pepper, and blue gum (Eucalyptus). Emanuel Fritz (1937) has, on several occasions, found this sapsucker attacking redwood trees. “In each instance the individual tree was ‘peppered’ with holes in horizontal rows, from the base to the top. In virgin timber, it is only an occasional tree that is attacked, and one searches in vain for another victim in the general vicinity. * * *