HABITS
The black-and-white warbler is one of the earliest spring warblers to reach its breeding-ground in the Transition Zone. Most of the other members of this family arrive in or pass through the region in mid-May or somewhat later, according to the season, when the oaks are in bloom and the opening flowers attract swarms of insects.
The black-and-white warbler, however, owing to its peculiar habit of feeding on the trunks and the large limbs of the trees, does not have to wait for the bounty supplied by the oaks but finds its special feeding-ground well stocked with food long before the oaks blossom or their leaves unfold. It comes with the yellow palm warbler late in April, when many of the trees are nearly bare, and not long after the pine warbler.
Mniotilta is a neat little bird, dressed in modest colors, at this season singing its simple but sprightly song as it scrambles over the bark—the black-and-white creeper, Alexander Wilson calls it.
Milton B. Trautman (1940), speaking of the spring migration at Buckeye Lake, Ohio, shows that the male birds are preponderant in the earliest flights. He says: “The first spring arrivals, chiefly males, were noted between April 16 and 30, and between May 1 and 5, 2 to 15 birds, mostly males, could be daily noted. The peak of migration usually lasted from May 6 to May 18, and then from 3 to 42 individuals, consisting of a few old males and the remainder females and young males, were daily observed. On May 18 or shortly thereafter a decided lessening in numbers occurred, and by May 23 all except an occasional straggler had left.”
Courtship.—Forbush (1929) gives this hint of courtship, which resembles the activities of most warblers at this season: “When the females arrive there is much agitation, and often a long-continued intermittent pursuit, with much song and fluttering of black and white plumage, and much interference from rival males before the happy pair are united and begin nesting.”
Nesting.—The black-and-white warbler usually builds its nest on the ground, tucking it away against a shrub or tree, or even under the shelter of an overhanging stone or bank. The nest is generally concealed among an accumulation of dead leaves which, arching over it, hides it from above. It is made, according to A. C. Bent (MS.), “of dry leaves, coarse grass, strips of inner bark, pine needles and rootlets, and is lined with finer grasses and rootlets and horsehair.” I have seen a nest made chiefly of pine needles on a base of dry leaves.
Henry Mousley (1916), writing of Hatley, Quebec, mentions moss as a component part of the nest, and says of three nests that they were all “heavily lined with long black and white horse hairs,” a peculiarity of coloration mentioned in one of Mr. Bent’s nests. Thomas D. Burleigh (1927b) speaks of a nest in Pennsylvania “built of dead leaves and rhododendron berry stems, lined with fine black rootlets and a few white hairs.” H. H. Brimley (1941) describes an exceptional nest. He says: “There was no particular departure from normal in its construction except for the fact that it was lined with a mixture of fine rootlets and very fine copper wire, such as is used in telephone cables. Fragments of such cable, discarded by repair men, were found nearby where a telephone line ran through the woods.”
Cordelia J. Stanwood (1910c) speaks of a nest “built in a depression full of leaves, behind a flat rock. * * * The cavity was shaped on a slant, the upper wall forming a partial roof. * * * It looked not unlike a small-sized nest of an Oven-bird. On the inside, the length was 21⁄2 inches, width 11⁄2 inches, depth 2 inches. On the outside, length 31⁄2 inches, width 21⁄2 inches, depth 21⁄2 inches. Thickness of wall at the top of nest, 1 inch; at the bottom, 1⁄2 inch.” Henry Mousley (1916) gives the average dimensions of three nests as “outside diameter 33⁄4, inside 13⁄4 inches; outside depth 21⁄4, inside 11⁄2 inches.”
F. A. E. Starr (MS.) writes to A. C. Bent from Toronto, Ontario, that all the nests he has found have been in broken-off stumps in low woods. “The cavity in the top of the stump,” he says, “is filled with old leaves, and the nest proper is made chiefly of strips of bark with grass and fiber.” Guy H. Briggs (1900) reports a nest “in a decayed hemlock stump, fifteen inches from the ground.” In such cases, of course, while the nest is well above the ground level, it rests on a firm foundation.