Mr. Burns’s data show that the height of the nest from the ground varies in middle and eastern States from 2 to 60 feet, and in central western States from ground level to 90 feet. His accumulated data on the measurements of nesting cavities show that the depth of the excavation is “greatest in New York and New England (10 to 36 inches), Illinois (14 to 24 inches), Pennsylvania (10 to 18 inches), and Minnesota (9 to 18 inches).” Probably the depth of the cavity depends on the quality of the wood and the age of the nest; when an old cavity is used, it is usually deepened somewhat. Dr. H. C. Oberholser (1896) gives the measurements of four Ohio nests; the total depth varied from 7 to 18 inches; the diameter of the entrance varied from 2.00 by 2.00 to 4.00 by 4.00 and averaged 2.94 by 2.72 inches. Mr. Burns (1900) says the diameter of the cavity near the bottom varies from 4.50 to 10.00, and averages 7.67 inches. No nesting material is taken in from outside, but enough fine chips are left in the bottom of the hole to make a soft bed, in which the eggs are partially buried. Carl W. Buchheister tells me that he once found a nest “the bottom of which was 6 inches below the ground level and 12 inches below the opening, a round hole which was 6 inches above the ground. There was but one egg.”
Eggs.—The flicker is notorious as a prolific egg layer, but under ordinary circumstances, when not disturbed, the average set consists of six to eight eggs. Incubated sets of as few as three or four have been found, sets of nine and ten are not very rare, and as many as 17 have been found in a nest at one time; the large numbers may be products of two females. Mr. Burns (1900) records the contents of 169 sets of the northern flicker as 11 sets of four, 16 sets of five, 35 sets of six, 34 sets of seven, 38 sets of eight, 17 sets of nine, 13 sets of ten, 3 sets of twelve, and one each of thirteen and fourteen. Major Bendire (1895) states that Steward Ogilby, of Staten Island, N. Y., reports “finding a brood of not less than nineteen young Flickers in one nest, all alive and apparently in good condition.”
If robbed of its eggs, the flicker will continue to lay new sets for a long time. Dr. Barton W. Evermann (1889) “obtained thirty-seven eggs in forty-nine days from a ‘yellowhammer’ which had its nest near my house. The eggs were in seven sets, five, five, five, six, seven, four, and five eggs respectively.” J. Parker Norris (1888) took five sets of six eggs each from a nest in Pennsylvania between May 16 and June 18. Several other similar cases of persistent laying have been reported, all of which indicate that an egg is laid each day and that the birds begin at once to replace the lost set. Mr. Burns (1900) lists a number of such cases, where no nest egg was left to induce the bird to keep on laying; the largest number reported was 48 eggs in 65 days. My neighbor, Charles L. Phillips, tried the experiment of taking one egg each day, leaving one as a nest egg; he holds the extraordinary record of having taken 71 eggs from one nest in 73 days; the poor bird rested only two days in the long strain of over two months.
Eggs of the flicker have sometimes been found in the nests of other birds. In an old orchard, not far from my home, I once found a flicker’s egg in a bluebird’s nest, with five eggs of the latter; and in another cavity in the same tree was a tree swallow’s nest containing five eggs of the swallow and an egg of the flicker. As this was in a remote locality, it is hardly likely that the eggs were placed there artificially, and the chances are that the flicker’s nest had been destroyed and she was forced to lay in the nearest available cavity. Mr. Burns (1900) says: “A similar instance is recorded by E. G. Elliot, Bradford, Mass., May 16th, ’84, of a set of five eggs of bluebird and one of flicker, nest of grass and feathers. Records of European house sparrow and red-headed woodpecker eggs in freshly excavated quarters with one or more eggs of the Flicker are not uncommon, and upon investigation the latter proved to be the aggrieved party in every instance.” He also tells of a flicker that laid an egg in a mourning dove’s nest.
The eggs of the flicker are pure lustrous white, with a brilliant gloss; the shell is translucent, and, when fresh, the yolk shows through it, suffusing the egg with a delicate pinkish glow, which is very beautiful.
The shape is quite variable, but the majority are ovate; some are short-ovate or elliptical-ovate, some nearly oval, and some rarely somewhat pointed. The measurements of 57 eggs average 26.85 by 20.58 millimeters; the eggs showing the four extremes measure 30.48 by 22.86, 28.19 by 24.38, 24.45 by 21.34, and 27.68 by 19.05 millimeters.
Young.—The period of incubation of the flicker has been said to be from 14 to 16 days. Miss Sherman’s (1910) careful observations on marked eggs, laid on known dates, indicate a shorter period. From some former nests she had learned “that sometimes the eggs hatched in nine days, but more frequently in ten days after the laying of the last egg.” In these cases, incubation may have begun before the set was complete, or the eggs may have received some heat from the body of the male, for she said that, in at least one case, “while the eggs were being laid, and before incubation began the male roosted in the box with the eggs.” According to a later observation, “the exact time for incubation had been twelve days, three hours and fifty-two minutes. The seventh egg hatched four hours later making its period of incubation eleven days and eight hours nearly.” After another similar experience with the hatching of nine marked eggs, which extended over a period from 5:40 a. m. one day until 10:48 a. m. the next day, she says: “Roughly speaking, then, the time that our Flickers take for incubation is from eleven to twelve days.”
Her observations showed that the duties of incubation are shared by both sexes, that the male usually incubates during the night, but “by day the duties of incubation seem to be shared about equally between the two birds, who are close sitters, the eggs seldom being found alone. Of the length of the sittings no adequate record has been kept, but those lasting from one hour and a half to two hours have been noted.”
Miss Sherman (1910) noted that “the usual time for depositing the eggs in the nest appears to be the hour between five and six o’clock in the morning,” though in one case an egg was laid between 11 a. m. and 4 p. m.
Some of her observations on the young follow: