This was about two weeks before the local breeding race (D. a. nigrifrons) might be expected to arrive.
Dr. Merrill (1888), at Fort Klamath, Oreg., found Audubon’s warblers “extremely abundant during the migrations. A few males were seen at Modoc Point on the 8th and 9th of April, and at the Fort on the 15th; by the 20th they were quite plentiful. A second ‘wave’ composed of both males and females, which latter had not previously been seen, arrived about the 4th of May, when they suddenly became more abundant than ever, bringing D. aestiva morcomi and H. lutescens with them.”
Nesting.—The only two nests of Audubon’s warbler that I have seen were shown to me in Washington, near the State University at Seattle. The University is located on high land at the north end of Lake Washington, where the steep banks, sloping down to the lake, are heavily wooded with a mixed growth of large and small firs of at least two species, as well as cedars, alder trees, and maples. In the more open part of the woods I was shown, on April 29, 1911, a nest of this warbler placed about 30 feet from the ground on two small branches and against the trunk of a tall Douglas fir beside a woodland path. The other nest I saw in the previously described “prairie region” near Tacoma on May 14, 1911; it was placed only 9 feet from the ground but 10 feet out from the trunk of a dense Douglas fir growing in the open, and was well concealed in the thick foliage.
These nests were evidently typical for the region, according to Rathbun. He mentions in his notes two other nests. One, found May 2, 1909, on the east side of Lake Washington and along a road, was 30 feet from the ground in a small hemlock, near the extremity of one of the limbs and 7 feet out from the trunk. The other, found May 11, 1913, was in a small fir about 30 feet up and about 4 feet from the trunk on one of the lower limbs. “The nest is a very beautiful structure, constructed outwardly of very small twigs from the fir or hemlock, inside of which are placed smaller ones of the same character, with black rootlets, and lined with feathers, of which a quantity are used, and a few horsehairs. It is a compactly built affair.” Dawson and Bowles (1909) say that the nests are placed from 40 to 50 feet up, and usually measure 4 inches in width outside by 23⁄4 in depth; and inside 2 by 11⁄2 inches. They are made externally of such materials as fir twigs, weed tops, flower pedicels, rootlets, and catkins, and are heavily lined with feathers of various birds—including grouse, ptarmigan or domestic fowls—these feathers often curving upward and inward so as partially to conceal the eggs.
Dr. J. C. Merrill (1898) found a very different type of nesting near Fort Sherman, Idaho: “Here a majority of the nests I found were in deciduous trees and bushes, generally but a few feet from the ground. One was in a small rose bush growing at the edge of a cut bank overhanging a road where wagons daily passed close to it. * * * Occasionally one was seen in deep woods by the roadside near where hay had been brushed off a load on a passing wagon; this was utilized for the entire nest except lining, making a conspicuous yellow object in the dark green fir or pine in which it was placed.”
P. M. Silloway (1901) found a nest of Audubon’s warbler near Flathead Lake, Mont., that was 18 feet from the ground in a fork of a willow. “The fork containing the nest was in a main stem, upright, a number of feet below the leaf-bearing part of the tree, so that the nest was exposed quite fairly to view.” H. D. Minot (1880) found one at Seven Lakes, Colo., in an odd situation: “The nest, composed of shreds and feathers, with a few twigs without and hairs within, was built in a dead, bare spruce, about twenty feet from the ground, compressed between the trunk and a piece of bark that was attached beneath and upheld above, where a bough ran through a knot-hole, so compressed that the hollow measures 21⁄4 x 13⁄4, and 11⁄2 inches deep.” Dr. Chapman (1907) describes a nest from Estes Park, Colo., as “loosely constructed of weed-stems and tops, and strips of bark, lined with fine weeds and horse-hair.”
Mr. Woodbury (MS.) describes Utah nests as “compactly woven, cup-shaped structures, usually of fine grasses, plant fibers or shredded bark, lined with feathers or some substitute, and camouflaged with some fine stringy material holding bracts or other small particles in place.” He reports nests in such conifers as spruce, balsam, and ponderosa pine, and in aspen and oak.
J. Stuart Rowley writes to me: “In California, I have found several nests of this species in the San Bernardino Mountains and in the Mono County area in the northern part of the State. The nests I have found have all been beautifully made structures, securely fastened to small, low hanging branches of lodgepole pine, and placed about 10 to 12 feet from the ground.”
Dr. Grinnell (1908) records three nests, found in the San Bernardinos; one “was twenty feet above the ground in the thick foliage of a short drooping fir bough. It was compactly composed of weathered grasses, frayed-out plant fibres, and tail and wing feathers of juncos and other small birds. Internally it was thickly lined with mountain quail feathers, some of the chestnut-colored ones sticking above the rim conspicuously. This feather feature seems to be characteristic of Audubon warblers’ nests, as it was noticeably present in all that we saw.” Another nest was 25 feet from the ground in one of the lowest branches of a yellow pine. The third “was snugly tucked away in a small clump of mistletoe on an alder branch twelve feet above the ground.”