Wilson found them usually in open plains and thinly wooded tracts, searching most leisurely among the foliage, carefully examining every leaf or blade of grass for insects, uttering, at short intervals, a brief chirr. They did not appear to be easily alarmed, and he has known one of these birds to remain half an hour at a time on the lower branch of a tree, and allow him to approach the foot, without being in the least disturbed. He found their food consisted of winged insects and small caterpillars.
In 1858, Mr. John Cassin wrote me: “The Prairie Warbler certainly breeds in New Jersey, near Philadelphia. I have seen it all summer for the last twelve years, and have seen the young just able to fly, but never found the nest. It has a very peculiar note, which I know as well as I do the Catbird’s, having often followed and searched it out. It frequents cedar-trees, and I suspect breeds in and about them.”
Dr. Coues found the Prairie Warbler mostly a spring and autumn visitant in the vicinity of Washington, being quite abundant during those seasons. A few were observed to remain during the breeding-season. They arrive earlier than most of this family of birds, or about the 20th of April. He found them frequenting, almost exclusively, cedar-patches and pine-trees, and speaks of their having very peculiar manners and notes.
Both Wilson and Audubon were evidently at fault in their descriptions of the nest and eggs. These do not correspond with more recent and positive observations. Its nest is never pensile. Mr. Nuttall’s descriptions, on the other hand, are made from his own observations, and are evidently correct. He describes a nest that came under his observation as scarcely distinguishable from that of the D. æstiva. It was not pensile, but fixed in a forked branch, and formed of strips of the inner bark of the red cedar, fibres of asclepia, and caterpillars’ silk, and thickly lined with the down of the Gnaphalium
plantagineum. He describes the eggs as having a white ground, sharp at one end, and marked with spots of lilac-purple and of two shades of brown, more numerous at the larger end, where they formed a ring. He speaks of their note as slender, and noticed their arrival about the second week of May, leaving the middle of September.
At another time Mr. Nuttall was attracted by the slender, filing notes of this bird, resembling the suppressed syllables ’tsh-’tsh-’tsh-’tshea, beginning low and gradually growing louder. With its mate it was busily engaged collecting flies and larvæ about a clump of locust-trees in Mount Auburn. Their nest was near, and the female, without any precautions, went directly to it. Mr. Nuttall removed two eggs, which he afterwards replaced. Each time, on his withdrawal, she returned to the nest, and resorted to no expedients to entice him away.
Several nests of this Warbler have been obtained by Mr. Welch in Lynn. One was built on a wild rose, only a few feet from the ground. It is a snug, compact, and elaborately woven structure, having a height and a diameter of about two and a half inches. The cavity is two inches wide and one and a half deep. The materials of which the outer parts are woven are chiefly the soft inner bark of small shrubs, mingled with dry rose-leaves, bits of vegetables, wood, woody fibres, decayed stems of plants, spiders’ webs, etc. The whole is bound together like a web by cotton-like fibres of a vegetable origin. The upper rim of this nest is a marked feature, being a strongly interlaced weaving of vegetable roots and strips of bark. The lining of the nest is composed of fine vegetable fibres and a few horse-hairs. This nest, in its general mode of construction, resembles all that I have seen; only in others the materials vary,—in some dead and decayed leaves, in others remains of old cocoons, and in others the pappus of composite plants, being more prominent than the fine strips of bark. The nests are usually within four feet of the ground. The eggs vary from three to five, and even six.
The late Dr. Gerhardt found this bird the most common Warbler in Northern Georgia. There its nests were similar in size, structure, and position, but differed more or less in the materials of which they were made. The nests were a trifle larger and the walls thinner, the cavities being correspondingly larger. The materials were more invariably fine strips of inner bark and flax-like vegetable fibres, and were lined with the finest stems of plants, in one case with the feathers of the Great Horned Owl. In that neighborhood the eggs were deposited by the 15th of May.
In Massachusetts the Prairie Warbler invariably selects wild pasture-land, often not far from villages, and always open or very thinly wooded. In Georgia their nests were built in almost every kind of bush or low tree, or on the lower limbs of post-oaks, at the height of from four to seven feet. Eggs were found once as early as the 2d of May, and once as late as the 10th of June. The birds arrived there by the 10th of April, and seemed to prefer hillsides, but were found in almost any open locality.
In Southern Illinois, Mr. Ridgway cites this species as a rather rare bird among the oak barrens where it breeds. He also met with it in orchards in the wooded portions, in April, during the northward migration of the Sylvicolidæ.