Part 68

"The first song has notes on three different pitches. The first notes, three to nine but commonly four or five, are all on the same pitch, usually the highest; the next note, usually a major third lower, is the lowest; the next, and last, is between them. Such a song might be written sree sree sree sree sree tro tray, all the notes being of equal length. I have 34 records of this song, 23 of which follow this form. A few are arranged with the last note highest, or lowest, or on the same pitch as the first. The first notes are sometimes varied by alternating short and long notes or sometimes are united in a long trill.

"The second song consists of four or five notes only, with a definite time arrangement--3 2 1 1 or 3 2 1 1 1; that is, the first note is three times as long as the last and the second note twice as long. The third and fourth notes are on the same pitch, but the others are on different pitches, so that the song might be written treee tray to to, or a 5-note song treee tray tray to-to tay. The notes, as in the first song, are on three different pitches, but they vary in every possible way as to which note is highest and which lowest, so that there are six possible arrangements of these different pitches in a 4-note song where the last two notes are always on the same pitch. In my collection of 52 records of this song I have samples of all six, and of these 33 are of four notes, while only 19 have the fifth note added.

"Songs of this species vary from 1-1/5 to 2 seconds in length, the first song from 1-2/5 to 2 seconds, and the second 1-1/5 to 1-4/5 seconds. The pitch varies from F´´´to E´´´´, a half tone less than an octave. One peculiar song of the first type, however, was prefixed by a wren-like chatter that was pitched on B´´, but the remaining song was normal in pitch. Single songs average about one and a half tones in range, but the majority of the songs of the first type range two tones, and those of the second type two and a half tones.

"The song is to be heard from the first arrival of the species in migration until shortly after the first of August. In 14 seasons the average date of late song in Allegany State Park is August 2, the earliest is July 25, 1927, and the latest August 11, 1935 and 1937. While there is no regular revival of full song after the molt, there is occasional singing of a primitive character."

C. Russell Mason tells me of a song in which the high, musical note was given six times instead of the usual once. Francis H. Allen has heard some variations in the songs and has sent me these notes: "One bird added at the end of the familiar zee zee zee zoo zee a coda of an intricate and wrenlike quality, and sang this beautiful song constantly. Another introduced a trill after the second note of the 'trees, trees' song and ended it with a low note. Another bird sang a variant of the 'trees, trees' song, in which it substituted for the final high note a lower-pitched su-eet su-eet without the familiar z quality." He and Dr. W. M. Tyler heard one that "sang in addition to one of the characteristic songs of the species an entirely unrecognizable one that went something like ti-ti-ti-ti-ti-zp. The first five notes were very thin and slight with a very short pause before the last one, and the final note was a short emphatic buzz. Once this song ran into a characteristic song without a pause between." He refers to the ordinary call-note as a distinctive chet, suggesting that of the myrtle warbler, but thinner. "On the occasion in early June, I heard from a male bird a succession of chippering notes which I had formerly attributed to the young alone. He alternated these notes with singing."

Many other somewhat similar renderings have appeared in print, both in syllables and in human words, most of which seem to recall the song to mind. Some of the best of the wordings are trees, trees, murmuring trees and sleep, sleep, pretty one, sleep (Torrey, 1885); good Saint Theresa (Maynard, 1896); and take it, take it, leisurely (Stanwood, 1910b). Miss Stanwood pays this tribute to the charm of the song: "His voice is suggestive of the drowsy summer days, the languor of the breeze dreamily swaying the pines, spruces, firs, and hemlocks. It recalls the incense of evergreens, the fragrance of the wild strawberry, the delicate perfume of the linnea. No other bird voice is so potent to evoke that particular spell of the northern woods."

The black-throated green warbler is a most persistent singer. The Nices (1932) say that the first warbler "gave 466 songs in a single hour and more than 14,000 in the 94 hours of observation." According to Albert R. Brand (1938), the approximate mean number of vibrations per second in the song is 6,025, in the highest note 6,750 and in the lowest note 5,125. This compares with a mean of 8,900 for the black-polled warbler, which is the shrillest passerine bird song.

Field marks.--The conspicuous, bright yellow cheeks, the olive-green back, the prominent black throat, the two white wing bands, and the white outer webs of the lateral tail feathers will distinguish the male in breeding plumage. The female is duller and has less black, or none at all, on the throat. Young birds in the fall are much like the female. See the descriptions under Plumages.

Fall.--The fall migration of the black-throated green warbler begins during the latter part of August, continuing through September and often through much of October. It seems to be a reversal of the route followed in the spring. Similar haunts are frequented in the fall in the company of vast congregations of other species. A remarkable flight of various species of warblers was seen by Rev. W. F. Henninger in Scioto County, Ohio, an account of which is quoted by W. L. Dawson (1903) as follows:

On September 28, 1899, I ran into a company of warblers which I would place conservatively at two thousand individuals. It was like a regular army as it moved up a long sloping hillside, and with wonderful rapidity. The wind was blowing almost a gale from the north, and the birds allowed themselves to be urged before it in the direction of their ultimate retreat, like half-stubborn autumn leaves. Lisping, chipping, whirling, driving, they hurried on and I after at full speed, panting, and wishing devoutly for a better chance to identify the fleeing forms. Arrived at the top of the hill the army suddenly halted and when I arrived breathless I had time to note the arrangement by species, not rigid indeed, but sufficiently striking to command attention. In the center were seen Hooded Warblers and a sprinkling of Chestnut-sides. On either side of these in turn were Black-throated Greens and Sycamores, about two hundred of each; while the wings proper were held by Bay-breasts and Black-polls in enormous numbers. * * * As the birds deployed to feed the specific lines were not quite obliterated.

Winter.--The following notes are contributed by Dr. Alexander F. Skutch: "The black-throated green warbler is an abundant winter resident in the Central American mountains, where it is well distributed on both the Caribbean and Pacific slopes. In Guatemala, it winters from 1,000 to about 8,500 feet above sea-level, but is not abundant at either of these extremes of altitude. Farther south, in Costa Rica, it prefers slightly higher elevations. Here I have not recorded it between 2,000 and 2,900 feet, although the greater part of my bird-watching in the country has been done in this altitudinal belt. From 2,900 feet, where it is rare as a winter resident, it ranges up to nearly 10,000 feet. At this elevation, I found it abundant on the Volcán Irazú in late November. Less sociable than the Townsend warbler, it does not form flocks, and except during the actual period of migration, is more often seen alone than in the company of others of its kind.

"As a rule the black-throated green warbler arrives late, and has rarely been recorded before mid-October. But on August 9, 1933, I found a lone male in full nuptial plumage with a mixed flock of small resident birds in an open oak wood on the Sierra de Tecpán in the Guatemalan highlands. He sang his dreamy, unsubstantial song as he foraged along with his newly found companions. I saw only one other of his kind--or possibly it was the same individual again--before early October, when the species began to arrive on the Sierra de Tecpán in numbers.

"Another early arrival appeared on September 28, 1938, in the yard of the cottage I occupied at Vara Blanca, at an altitude of 5,500 feet on the northern slope of the Cordillera Central of Costa Rica. During the following days, it came every afternoon to forage in the low cypress hedges that surrounded the dwelling. Possibly it was attracted to these because of associations with its native land, for these trimmed cypresses were the only coniferous trees in the vicinity--indeed, in Costa Rica, the warblers find no native conifers save two species of Podocarpus, a genus whose center of distribution is in the Southern Hemisphere rather than in the North. At times the newly arrived warbler descended to the bare ground in the flower garden, where it appeared to find something edible. On October 2 it was for the first time accompanied by a second of its kind. Throughout the winter months a black-throated green warbler continued to visit these cypress hedges.

"This is another migrant warbler that plucks the dainty white protein corpuscles from the velvety cushions at the bases of the long petioles of the Cecropia tree. In excessively humid highland regions, as at Vara Blanca, the wide, hollow internodes of these trees are much of the time flooded with water, and therefore uninhabitable by the Azteca ants which at lower elevations usually colonize them. In the absence of the ants, whose food these tiny morsels are, the birds find an abundance of them on the Cecropia trees. A number of small native birds, including finches, tanagers, warblers, honeycreepers and ovenbirds (Furnariidae), share them with the migratory warblers.

"By mid-March the males are in resplendent nuptial plumage. On April 27, 1933, I heard a male black-throated green warbler singing among the alder trees beside a rivulet on the Sierra de Tecpán. On April 4 and 5, 1938, a male sang repeatedly at the edge of the forest at Vara Blanca; and from this date until the disappearance of the species from the region on April 14 I often heard their song.

"There is a certain amount of evidence that with the increasing aridity of the dry season the black-throated green warblers withdraw early in the year from districts on the Pacific slope where they were present during the wetter closing months of the preceding year. Thus, on the Sierra de Tecpán I met none between December 7 and April 20, when the northward movement was in progress, and the birds seen were doubtless transients rather than winter residents. And in the higher parts of the Basin of El General in southern Costa Rica I have recorded the species only in October, November, and December, after which the nearly rainless season begins. But in the wetter climate of Vara Blanca, they were seen throughout February and March until their northward departure in April.

"The black-throated green warbler withdraws from Costa Rica about the middle of April, and by the end of the first week of May has vanished from Guatemala.

"Early dates of fall arrival in Central America are: Guatemala--passim (Griscom), October 15; Sierra de Tecpán, August 9, 1933; Finca Mocá, October 29, 1934. Honduras--Tela, October 26, 1930. Costa Rica--Vara Blanca, September 28, 1937; San José (Underwood), October 16; Basin of El General, October 22, 1936.

"Late dates of spring departure from Central America are: Costa Rica--Juan Viñas (Carriker), April 17; Vara Blanca, April 14, 1938. Guatemala--passim (Griscom), May 4; Sierra de Tecpán, May 6, 1933."

The following account of its winter haunts in El Salvador by Dickey and van Rossem (1938) is also interesting:

All through the mountainous districts, both in the interior and coastwise, the black-throated green warbler is an extremely common winter visitant; in fact, it constitutes, at levels between 3,500 and 5,000 feet, fully 90 per cent of the nonresident warbler population. The numerous flocks of from a dozen to half a hundred individuals invariably formed the nuclei about which gathered smaller numbers of other insectivorous species resident and nonresident. The black-throated green warbler showed decided preference for the oak and pine association at the altitudes mentioned, although it was by no means confined to such environments.

Many were seen in the coffee cover down to 3,000 feet on Mt. Cacaguatique and 2,300 feet at San Salvador. A few birds reach as high as 8,000 feet, at which level they were found in both pines and cloud forest on Los Esesmiles. * * * The average winter range of virens lies approximately 3,000 feet below that of townsendi, although strays and vagrants make the extremes of altitude nearly the same in both cases.

DISTRIBUTION

Range.--Eastern North America from southern Canada to Panamá.

Breeding range.--The black-throated green warbler breeds =north= to central western and northeastern Alberta (Grande Prairie, Peace River and Chipewyan); central Saskatchewan (Big River and Emma Lake); southern Manitoba (Brandon and Hillside Beach); southern Ontario (Lac Seul, Rossport, Chapleau, and Lake Abitibi; casual or accidental at Moose Factory); central Quebec (Mistassini Post, Upper St. Maurice River, Godbout, Mingan, and Natashquan); and casually in southeastern Labrador (Battle Harbor). =East= to southeastern Quebec (Natashquan); southwestern Newfoundland (Spruce Brook and Tompkins); Nova Scotia (Sydney, Halifax, and Barrington); the coast of New England; Long Island (Miller's Place); northern New Jersey (Demarest and Dover); central Pennsylvania (Pottsville and Carlisle); central Maryland (Thurmont); central and southeastern Virginia (Charlottesville and Dismal Swamp); North Carolina (Lake Mattamuskeet); and central South Carolina (Charleston). =South= to South Carolina (Charleston); northern Georgia (Pinelog Mountains and Lookout Mountain); northeastern Alabama (Sand Mountain); southeastern Kentucky (Big Black Mountain and Jackson); central Michigan (Bay City and Mason County); northern Wisconsin (New London and Ladysmith); central Minnesota (Lake Minnetonka, Mille Lacs, and Cass Lake); southwestern Manitoba (Aweme); and southern Alberta (Brooks). =West= to western Alberta (Brooks, Glenevis, Sturgeon Lake, and Grande Prairie).

Winter range.--The black-throated green warbler is found in winter =north= to southern Texas (Arroya Colorado, Willacy County); and Yucatán (Tunkas and Chichén-Itzá). =East= to Yucatán (Chichén-Itzá); the coast of Quintana Roo; northeastern El Salvador (Mount Cacaguatique); eastern Costa Rica (Volcán Irazú); and central Panamá (Veragua); casual or accidental to northern Colombia (one record; Cincinnati, Santa Marta region). =South= to Panamá (Veragua and Volcán de Chiriquí). =West= to western Panamá (Volcán de Chiriquí); western Costa Rica (El General); western El Salvador (San Salvador); western Guatemala (Volcán de Agua and Dueñas); Oaxaca (Tehuantepec); western Morelos (Curnavaca); Puebla (Metlatoyuca); southern Tamaulipas (Altamira); probably eastern Nuevo León (Linares); and southern Texas (Santa Maria and Arroya Colorado).

The black-throated green warbler has apparently extended its winter range northward in recent years. Except for a single specimen taken at Brownsville in January 1911, it was not known to winter in Texas until 1933-34, when about 30 birds were seen. Since then it has increased and spread over most of Cameron County and to the southern border of Willacy County. One was recorded on Bull's Island, S. C., on January 8 and 9, 1940.

The species is also rare or casual in winter or migration in the West Indies: Cuba (Habana and Isle of Pines); Jamaica; Haiti (Île à Vache); Puerto Rico (Adjuntas); and the islands of St. Croix, Guadeloupe, and Dominica; also Watling Island, Bahamas.