The Prebles (1908) found it well distributed and probably breeding throughout the Athabaska-Mackenzie region. MacFarlane (1908) found it breeding as far north as the Anderson River. Kennicott, according to Baird, Brewer, and Ridgway (1874), found it nesting about Great Slave Lake. And Ernest Thompson Seton (1891) reported it as a common summer resident and breeding near Carberry, Manitoba.
Nesting.—Herbert Brandt (1943) found two nests of the eastern orange-crowned warbler along the Yukon River in Alaska, about 20 miles up from the sea, on July 1, 1924. His first nest contained five eggs, advanced in incubation. The nest was near the bank of the river, “in a bush 18 inches from the ground. The nest was loosely made of coarse grass held together with bark strips, silvery plant down, and a few feathers, one of which was a mottled feather of the Northern Varied Thrush. Twenty feet away was another nest of the same species, which held three young just hatched and two pipped eggs. * * * The measurements of the two nests cited are: height, 2.25 to 3.00; outside diameter, 3.5; inside diameter, 1.75; and depth of cup, 1.50 to 1.75 inches.”
MacFarlane’s (1908) nests, found on the Anderson River, “held from four to six eggs each, and they were made of hay or grasses lined with deer hair, feathers and finer grasses, and were usually placed in a shallow cavity on the ground in the shade of a clump of dwarf willow or Labrador tea.”
Baird, Brewer, and Ridgway (1874) write:
The nests of this species, seen by Mr. Kennicott, were uniformly on the ground, generally among clumps of low bushes, often in the side of a bank, and usually hidden by the dry leaves among which they were placed. He met with these nests in the middle of June in the vicinity of Great Slave Lake. They were large for the size of the bird, having an external diameter of four inches, and a height of two and a half, and appearing as if made of two or three distinct fabrics, one within the other, of nearly the same materials. The external portions of these nests were composed almost entirely of long, coarse strips of bark loosely interwoven with a few dry grasses and stems of plants. Within it is a more elaborately interwoven structure of finer dry grasses and mosses. These are softly and warmly lined with hair and fur of small animals.
E. A. Preble (1908) reported a nest found near Fort Resolution that “was placed among thick grass on a sloping bank, and was composed outwardly of grass and Equisetum stems, with a layer of finer grass and with an inner lining of hair.”
Several nests have been reported from points farther south as being of this warbler, but these are probably all referable to the Rocky Mountain subspecies Vermivora celata orestera.
Eggs.—The orange-crowned warbler lays from 4 to 6 eggs to a set, probably most often 5. Dr. Brandt (1943) describes his Alaska eggs as follows: “The egg is short ovate in outline, the surface moderately glossy, and the shell delicate. The ground color is white and is prominent because the markings obscure but one-fifth of its area. These spots are very small, and are peppered over the broad end in an ill-defined wreath, while over the smaller two-thirds the egg is almost immaculate. In color the markings range from hydrangea red to ocher red; and underlying these are a few weak spots of deep dull lavender.” Probably a series of the eggs would show all the variations shown in eggs of the other races. The measurements of 50 eggs, including those of the Rocky Mountain race, average 16.2 by 12.7 millimeters; the eggs showing the four extremes measure 18.3 by 13.2, 17.0 by 14.2, and 14.7 by 12.2 millimeters (Harris).
Plumages.—Dr. Dwight (1900) describes the juvenal plumage as “above, brownish olive-green. Wings and tail olive-brown, broadly edged with bright olive-green, the median and greater coverts tipped with buff. Below, greenish buff paler and yellower on abdomen and crissum. Lores and auriculars grayish buff.”
The first winter plumage is acquired by a postjuvenal molt that involves the contour plumage and the wing coverts but not the rest of the wings or the tail. The sexes are alike in the juvenal plumage and much alike in all plumages, except that the female is always duller; in her first winter plumage the orange crown is lacking, and it is more or less suppressed and sometimes wholly lacking in subsequent plumages. Dr. Dwight (1900) describes the young male in first winter plumage as “above, bright olive-green, mostly concealed on the pileum and nape with pale mouse-gray edgings that blend into the green. The crown brownish orange concealed by greenish feather tips. Wing coverts broadly edged with dull olive-green, sometimes the greater coverts with faint whitish tips. Below, pale olive-yellow, grayish on the chin and sides of neck with very indistinct olive-gray streaking. A dusky anteorbital spot. Lores, orbital ring and indistinct superciliary stripe mouse-gray.”