Life histories of North American woodpeckers

by Arthur Cleveland Bent

It nests at varying distances from the ground from 8 to 40 feet, generally at heights of about 15 feet. I have the indurated form of a nesting cavity of this species now before me, showing its exact shape. The hardened walls are about one-fourth of an inch thick, and show the inner contour of the cavity perfectly. The entrance is nearly 3 inches in diameter; inside it is about 7 by 4 inches wide and 5½ inches deep. The sides and bottom of the cavity are quite smooth, considering the nature of the substance (the soft inner pulp of the cactus) out of which it is excavated. It occupied only one-half of the trunk of one of these giant cacti, and the rear of the cavity did not quite reach the center of the plant. The eggs lay on the hardened floor, and not, as usual, on a layer of chips. I am inclined to believe that a freshly excavated nesting site is not habitable for some weeks, as it must require some time for the exuding sap to harden. The mold before me somewhat resembles a wasp’s nest, both in color and shape, and if suspended from the limb of a tree might easily be mistaken for one.

Eggs.—As to the number of eggs laid by the gilded flicker, Mr. Gilman (1915) writes: “Of the twenty-seven nests examined, eight had five eggs, or young plus eggs, to make count of five for the set; eleven had four eggs or young, or young plus eggs; six nests contained three eggs or three young; and two nests had two young each. In no case did I find five young in a nest, and from the fact that infertile eggs were found with three and four young in a nest, it may be inferred that in many of the nests containing two, three or four young, more eggs had been laid. In no nest did I find more than five eggs, and I conclude that the set is from three to five eggs.”

The gilded flicker evidently lays fewer eggs than its northern and eastern relatives, and the surprising thing is that there are so many cases of infertile eggs, often one and sometimes two in a set. I have had sets of six and seven eggs reported in collections, but these may have been products of two females, where nesting holes were scarce or the region overcrowded by the many birds that use these holes. The few eggs that I have seen are like other flickers’ eggs but either dull white or only slightly glossy; this may not be the universal rule, however. The measurements of 50 eggs average 27.86 by 21.34 millimeters; the eggs showing the four extremes measure 32.0 by 22.0, 27.78 by 22.22, and 24.61 by 20.04 millimeters.

Plumages.—Mr. Gilman (1915) says: “The young when first hatched are not very prepossessing to any one, except perhaps the parents. At first glance they remind one of the pictured restoration of the Plesiosaurus, with their long twisting naked necks. The lower mandible was more than an eighth of an inch longer than the upper, and on the tip of each was the hard white growth used in opening the shell.”

In the juvenal plumage, which is acquired before the young bird leaves the nest, the young male is similar to the adult male, but the forehead is usually tinged with dark red; the red malar patch is duller and less uniform; the upper parts are grayer, less brownish, and more heavily barred; the primaries are tipped with brownish white; the under parts are grayish white, more profusely, but less distinctly, spotted; the black patch on the breast is smaller and more central; the yellow in the wings and tail is duller; the black tips on the under side of the tail are duller and not so well defined; and the bill is much smaller and weaker. The young female is similar to the young male, but there is no red in the crown or in the malar patches, the latter being pale brown.

I have not seen enough material, taken at the proper seasons, to work out the molts, but these are probably the same as in other flickers.

Several apparent hybrids with cafer have been reported. Dr. Grinnell (1914), who has made a study of this subject, seems to doubt if there is any hybridizing between these species; he writes:

The salient fact shown by this comparative examination is that in all other characters the specimens aberrant in colors of wing and tail, are perfectly typical of chrysoides (that is, of its subspecies mearnsi). None of the phenomena consequent upon hybridization is evidenced in other particulars, such as general size, proportional dimensions, extent of dorsal barring, colors of body and head. In all these characters there is no nearer approach of the red-shafted chrysoides to collaris, than of the yellow-shafted chrysoides.

My conclusion is that the strain of chrysoides occurring at the present time in the lower Colorado Valley shows proneness to replacement of yellow by red, without there having been any interbreeding with another species. This may be accounted for chemico-physiologically, as in the case of the linnet of the Hawaiian Islands, where, however, the change has been from red to yellow.

* * * It is quite evident that the aberrant examples described by Brewster and Swarth from central Arizona, as referred to above, are of the same nature as the Colorado Valley specimens. The chances are that they were not hybrids. So far as shown by the literature at hand, no unquestioned hybrids have been found between chrysoides (or any of its subspecies) and collaris or cafer.