In the spring of 1906, W. W. Brown, Jr., with two assistants, collected for two months on the island for the Thayer Museum, of which Thayer and Bangs (1908) say: “This well-marked island form is in all probability doomed to speedy extinction, and will be the next of the Guadalupe birds to go. Brown and Marsden found in all not more than forty individuals in the island. In the small cypress grove near the cabins there were four and in the large cypress woods about thirty-five.
“Mr. Brown tells us that in the breeding season, at least, the species is wholly confined to the cypresses, none being seen in the pine woods. The bird is very tame and unsuspicious and falls an easy prey to the cats.”
Courtship.—Mr. Bryant (1887) noted Guadalupe flickers in courtship antics in January and in February. According to his description of their actions and their notes at such times, these performances are evidently similar to those of other flickers elsewhere.
Nesting.—Apparently Dr. Palmer found no nests and collected no eggs of this flicker, but Mr. Bryant (1887) has this to say about its nesting habits:
By March 16, the birds were invariably found in pairs, and my wish to secure a setting of eggs before departing seemed in a fair way of being fulfilled. Strolling among the cypresses on the 27th of March, I found four trees upon which the birds were at work or had been recently, and in such cases the birds themselves were always to be found in the immediate vicinity. Passing a half-dead tree I heard the sounding taps of a woodpecker at work, and as I neared the spot, the slight noise which I made as I carefully picked my way over the rock-strewn ground caused a handsome male bird to suddenly appear at an opening about four feet high. With a foot grasping either side of the entrance he gazed upon the intruder. Having comprehended the situation, he flew to another tree, where he quietly awaited my inspection and departure. The hole was then down about fifteen inches. By April 7, it had reached a depth of about twenty inches and contained six fresh eggs, upon which the female was then sitting.
Mr. Brown collected, for the Thayer Museum, six sets of eggs, one set of five, two sets of four, one set of three, and two single eggs, all of which are now in the Museum of Comparative Zoology in Cambridge, Mass. The eggs were collected on dates ranging from May 8 to June 8, 1906; the nests were all in cypresses, mostly old or dead trees or stumps, at heights ranging from 4 to 20 feet above the ground, and at altitudes of from 3,700 to 4,500 feet above sea level; one of the cavities was only 2 inches deep, but some of the others were 18 or 20 inches deep and from 3½ to 4 inches in diameter.
Eggs.—The number of eggs laid by the Guadalupe flicker apparently ranged from four to six. The eggs that I have seen, in Cambridge, are ovate, pure white, and decidedly glossy, like other flickers’ eggs. The measurements of 23 eggs average 27.8 by 21.7 millimeters; the eggs showing the four extremes measure 30.2 by 21.1, 28.0 by 22.5, and 26.8 by 20.5 millimeters.
Food.—Mr. Bryant (1887) says: “The food of this species during a portion of the year consists largely of smooth-skinned caterpillars, besides numerous beetles and ants; the latter are always obtainable and growing to a large size figure as an important item of their diet.”
Behavior.—He also remarks: “Of all the species of this family I have ever met with, none have been so tame and unsuspicious or less frightened by the report of a gun.”
Voice.—The notes of the Guadalupe flicker are also similar to those of the mainland forms, for Mr. Bryant (1887) says: “In addition to the familiar scythe-whetting notes they have the peculiar ‘wake-up’ call and its rapid prelude of monosyllables. By imitating this call I decoyed a distant female to within short range, the bird coming through the thickest of the cypress grove, stopping at short intervals to call and listen for a reply.”