Part 7

In its excursions over the trunks and larger limbs of trees the Black and White Creeper is certainly not looking for vegetable food, and only a trace of such matter has been found in the stomachs examined. The food is chiefly insects but considerable numbers of spiders and daddy-long-legs also are eaten. Beetles, caterpillars, and ants are the larger classes of insect food, but moths, flies, bugs, and a few hymenoptera also are eaten. Among forest enemies that have been found in stomachs of this species are round-headed wood borers, leaf beetles, flea beetles, weevils, bark beetles, leaf hoppers, and jumping plant lice. The hackberry caterpillar, the hackberry psyllid, an oak leaf beetle Xanthonia 10-notata, and the willow flea beetle, are forms specifically identified. Observers have reported this warbler to feed also upon ordinary plant lice, and upon larvae of the gypsy moth.

Forbush (1929) adds the following observation: "The food of this bird consists mostly of the enemies of trees, such as plant-lice, scale-lice, caterpillars, both hairy and hairless, among them such destructive enemies of orchard, shade and forest trees as the canker-worm and the gipsy, brown-tail, tent and forest tent caterpillars. Wood-boring and bark-boring insects, click beetles, curculios and many other winged insects are taken. Sometimes when the quick-moving insects escape its sharp bill, it pursues them on the wing but most of its attention is devoted to those on the trees."

H. H. Tuttle (1919), speaking of the male parent feeding the young birds, says: "The fare which he provided was composed entirely of small green caterpillars, cut up into half-lengths."

Behavior.--The black-and-white warbler seems set apart from others of the group, perhaps because of its marked propensity for clambering over the trunks of trees and their larger branches. Although, like other warblers, it seems at home among the smaller twigs, it spends a large part of its time on upright surfaces over which it moves easily and quickly, upward, downward, and spirally, with great agility and sureness of footing, constantly changing direction, and not using the tail for support. As it scrambles over the bark, it switches from side to side as if at each hop it placed one foot and then the other in advance, and even on slim branches it hops in the same way, the tail alternately appearing first on one side of the branch and then on the other; it reminds us of a little schoolgirl swishing her skirt from side to side as she walks down the street. The bird is alert and watchful, and if it starts an insect from the bark, or sees one flying near, it may pursue it and catch it in the air.

H. H. Tuttle (1919) describes an extreme example of behavior simulating a wounded bird. He says: "She struck the leaves with a slight thud and turned over on her side, while the toes of one up-stretched leg clutched at the air and her tail spread slowly into a pointed fan. * * * Deceived for a moment then, I turned a step in her direction. She lay quite still except for a quivering wing. I reached out toward her with a small stick and touched her side; she screamed pitifully; I stretched out my hand to pick her up, but with a last effort she righted herself, and by kicking desperately with one leg, succeeded in pushing forward a few inches."

We associate this warbler with dry, rocky hillsides where the ground is strewn with dead leaves, but the bird may breed also in the dry portions of shady, wooded swamps.

Voice.--The black-and-white is one of the high-voiced singers. Its song is made up of a series of squeaky couplets given with a back-and-forth rhythm, a seesawing effect, like the ovenbird's song played on a fine, delicate instrument. It may be suggested by pronouncing the syllables we see rapidly four or five times in a whispered voice. In the distance the song has a sibilant quality; when heard near at hand a high, clear whistle may be detected in the notes. The final note in the song is the accented see.

Albert R. Brand (1938), in his mechanically recorded songs of warblers, placed the black-and-white's song as the fourth highest in pitch in his last of 16 species, the black-poll, blue-winged, and the Blackburnian being higher. He gives the approximate mean (vibrations per second) of the black and white as 6,900 and of the blackpool as 8,900.

Aretas A. Saunders (MS.) says: "The pitch of the songs varies, according to my records, from B´´´ to E´´´´, a range of three and a half tones more than an octave. A single song, however, does not vary more than three and a half tones."

A second song, not heard, I think, until the bird has been on its breeding ground for some time, is rather more pleasing, less monotonous, than the first. It is longer, somewhat faster, more lively, and is modulated in pitch. Francis H. Allen (MS.) speaks of it thus: "Later in the season a more elaborate song is very commonly heard. I have been accustomed to syllabify it as weesy, weesy, weesy, weesy, woosy, woosy, weesy, weesy. The notes indicated by woosy really differ from the others only by being pitched lower."

Occasionally we hear aberrant songs which prove puzzling until we can see the singer. Allen remarks that he has heard several such songs, and I remember hearing one in which the lower note of each couplet was reduplicated, thereby strongly suggested one of the songs of the Blackburnian warbler. Sometimes Mniotilta sings during flight. I once heard a song from a bird flying within a few feet of me--at this range a sound of piercing sharpness.

Of the minor notes Andrew Allison (1907) says: "I know of no other warbler except the Chat that can produce so great a variety of sounds; and since nearly all of the notes resemble those of other warblers, this is a most confusing bird to deal with during the busy season of 'waves'."

The call note often has a buzzing quality, and often runs into a long chatter (also characteristic of the young bird), but it may be given so sharply enunciated that it suggests the chip of the black-poll. Allen (MS.) writes it chi, "like pebbles struck together," and Cordelia J. Stanwood (1910) renders it sptz, saying "the sound resembled the noise made by a drop of syrup sputtering on a hot stove."

Field marks.--The black-poll, in its spring plumage, and the black-and-white warbler resemble each other in coloration, but the latter bird may be readily distinguished by its white stripe down the center of the crown and the white line over the eye. The contrast in the behavior of the two birds separates them at a glance.

Enemies.--Like other birds which build on the ground, the black-and-white is subject, during the nesting season, to attacks by snakes and predatory mammals. A. D. DuBois (MS.) cites a case in which maggots destroyed a nestful of young birds.

Harold S. Peters (1936) reports that a fly, Ornithoica confluens Say, and a louse, Myrsidea incerta (Kellogg), have been found in the plumage of the black-and-white warbler.

Herbert Friedmann (1929) says: "This aberrant warbler is a rather uncommon victim of the Cowbird, only a couple dozen definite instances having come to my notice. * * * The largest number of Cowbirds' eggs found in a single nest of this Warbler is five, together with three eggs of the owner." George W. Byers (1950) reports a nest of this warbler, in Michigan, that held two eggs of the warbler and eight of the cowbird, on which the warbler was incubating. His photograph of the eggs suggests that they were probably laid by four different cowbirds.

Fall.--Several of the warblers show a tendency to stray from their breeding grounds soon after their young are able to care for themselves, perhaps even before the postnuptial molt is completed and long before the birds gather into the mixed autumn flocks. Among these early wandering birds the black-and-white warbler is a very conspicuous species, perhaps because it is one of our commoner birds or, more probably, because of its habit of feeding in plain sight on the trunks and low branches of dead or dying trees and shrubs instead of hiding, like other warblers, high up in the foliage. It may be that the warblers we see at some distance from their breeding grounds thus early in the season have already begun their migration toward the south: they often appear to be migrating.

Behind the house in Lexington, Mass., where I lived for years, there was a little hill, sparsely covered with locust trees, to the southward from my dooryard. This hill was a favorite resort for warblers in late summer. No warbler bred within a mile of the spot, except the summer yellowbird, to use the old name, yet soon after the first of July the black-and-white warblers began to assemble there. Not infrequently I have seen a single bird come to the hill, flying in from the north across Lexington Common, and join others there. The small company might remain for an hour or more, frequently singing (evidently adult males) as the birds fed in the locust trees.

Later in the season, as August advances, migration appears more evident. The birds now gather in larger numbers, sometimes as many as eight or ten; they pause in the locust trees for a shorter time before flying off; they are no longer in song; and the majority of the birds have white cheeks, most of them presumably young birds. Although they are almost silent as they climb about feeding, if you stand quietly in the midst of a company of four or five, now and then you may hear a faint note, and at once the note comes from all sides, each bird apparently reporting its whereabouts--a sound which calls to mind the south-bound migrants as they roam through the quiet autumn woods. Other warblers, unquestionably migrants, visit this hillside in August, notably the Tennessee, an early arrival who has already traveled a long way.

The fall migration of the black-and-white is long-drawn-out. The bird does not depend, like many of the warblers, on finding food among the foliage, so it may linger long after the trees are bare of leaves, sometimes, here in New England, well into October. I saw a bird in eastern Massachusetts on October 23, 1940, a very late date.

Winter.--Dr. Alexander F. Skutch (MS.) sent to A. C. Bent the following comprehensive account of the bird on its winter quarters: "None of our warblers is more catholic in its choice of a winter home than the black-and-white. Upon its departure from its nesting range, it spreads over a vast area from the Gulf States south to Ecuador and Venezuela, from the Pacific coast of Mexico and Central America eastward through the Antilles. And in the mountainous regions of its winter range it does not, like so many members of the family, restrict itself to a particular altitudinal zone, but on the contrary scatters from sea level high up into the mountains. As a result of this wide dispersion, latitudinal and altitudinal, it appears to be nowhere abundant in Central America during the winter months, yet it has been recorded from more widely scattered localities than most other winter visitants. On the southern coast of Jamaica, in December 1930, I found a greater concentration of individuals than I have ever seen in Central America during midwinter.

"Wintering throughout the length of Central America, from near sea level up to 9,000 feet and rarely higher, the black-and-white warbler is somewhat more abundant in that portion of its altitudinal range comprised between 2,000 or 3,000 and 7,000 or 8,000 feet above sea level. It is found in the heavy forest, in the more open types of woodland, among the shade trees of the coffee plantations, and even amid low second-growth with scattered trees. It creeps along the branches in exactly the same fashion in its winter as in its summer home. Solitary in its disposition, two of the kind are almost never seen together. The only time I have heard this warbler sing in Central America was also one of the very few occasions when I found two together. Early on the bright morning of September 1, 1933, when the warblers were arriving from the north, I heard the black-and-white's weak little song repeated several times among the trees at the edge of an oak wood, at an altitude of 8,500 feet in the Guatemalan highlands. Looking into the tree tops, I saw two of these birds together. Apparently they were singing in rivalry, as red-faced warblers, Kaup's redstarts, yellow warblers, and other members of the family solitary during the winter months will sing in the face of another of their kind, at seasons when they are usually silent. Often such songs lead to a pursuit or even a fight; but I have never seen black-and-white warblers actually engaged in a conflict in their winter home.

"Although intolerant of their own kind, the black-and-white warblers are not entirely hermits; for often a single one will attach itself to a mixed flock of small birds. In the Guatemalan highlands, during the winter months, such flocks are composed chiefly of Townsend's warblers; and each flock, in addition to numbers of the truly gregarious birds, will contain single representatives of various species of more solitary disposition, among them often a lone black-and-white, so different in appearance and habits from any of its associates.

"This warbler arrives and departs early. It has been recorded during the first week of August in Guatemala, and by the latter part of the month in Costa Rica and Panamá. In Costa Rica, it appears not to linger beyond the middle or more rarely the end of March; while for northern Central America my latest date is April 22.

"Early dates of fall arrival in Central America are: Guatemala--passim (Griscom), August 3; Sierra de Tecpán, August 23, 1933; Santa María de Jesús, August 6, 1934; Huehuetenango, August 14, 1934. Honduras--Tela, August 19, 1930. Costa Rica--San José (Cherrie), August 20; Carrillo (Carriker), September 1; San Isidro de Coronado, September 8, 1935; Basin of El General, September 19, 1936; Vara Blanca, September 5, 1937; Murcia, September 11, 1941. Panamá--Canal Zone (Arbib and Loetscher), August 24, 1933, and August 29, 1934. Ecuador--Pastaza Valley, below Baños, October 17, 1939.

"Late dates of spring departure from Central America are: Costa Rica--Basin of El General, February 23, 1936, March 10, 1939, March 26, 1940, March 3, 1942, March 18, 1943; Vara Blanca, March 13, 1938; Guayabo (Carriker), March 30; Juan Viñas (Carriker), March 21. Honduras--Tela, April 22, 1930. Guatemala--Motagua Valley, near Los Amates, April 17, 1932; Sierra de Tecpán, February 20, 1933."

The bird has a wide winter range, as shown above. Dr. Thomas Barbour (1943) speaks of it thus in Cuba: "Common in woods and thickets. A few arrive in August, and by September they are very abundant, especially in the overgrown jungles about the Ciénaga."