near Coatesville, Pa. A female specimen was collected September 17,
1939, at Gulfport, Miss. On August 18, 1934 one was reported seen at
East Hampton, Long Island; another was closely observed by several
competent observers in Prospect Park, Brooklyn, N. Y., May 8 to 10,
1947.
_Egg dates._--British Columbia: 2 records, June 7 and 24.
Oregon: 3 records, June 7 to 21.
Washington: 18 records, May 24 to June 24; 9 records, June 8 to 19,
indicating the height of the season (Harris).
DENDROICA VIRENS VIRENS (Gmelin)
NORTHERN BLACK-THROATED GREEN WARBLER
PLATES 36-38
HABITS
The northern black-throated green warbler I have always associated with
the white pine woods, the delightful fragrance of fallen pine needles
carpeting the forest floor, and the murmuring of the warm summer breeze.
The song has been written as "trees, trees, murmuring trees,"
appropriate words that seem to call vividly to mind the pretty little
bird in its sylvan haunts and its delicious and soothing voice.
In southeastern Massachusetts, from late April until after midsummer one
can seldom wander far in the thick groves of white pine (_Pinus
strobus_), either in the open stands or in mixed woods where these pines
predominate, without hearing the delightful drawling notes of this
warbler, though the tiny singer in the tree-tops is not so easily seen.
It is not, however, exclusively confined even in the breeding season to
such woods, for sometimes we find it in open stands of pitch pines
(_Pinus rigida_) or in old neglected pastures and hillsides where there
is a scattered growth of red cedars (_Juniperus virginiana_).
Gerald Thayer wrote to Dr. Chapman (1907) that, in the Monadnock region
of New Hampshire, the black-throated green warbler is "a very common or
abundant summer bird through all the region, high and low; ranging from
the pine woods of the lowest valleys to the half open copses of spruce
and mountain ash along Monadnock's rocky ridge--2,500 to 3,160 feet.
* * * Though decidedly a forest Warbler, it favors second growth, and
pasture-bordering copses, rather than the very heavy timber, and is
particularly partial to dry white pine woods."
Farther north, in the Canadian Zone, these warblers are at home in the
forests of spruce and fir, but even here they seem to prefer pines, if
they can find them, for Ora W. Knight (1908) says that in Maine "in the
breeding season they resort to the pine woods by preference, and as a
result are rather common in the pine barrens of the coastal plain.
Inland the species is common, and while preferring the pines still, also
occurs in rather open mixed woods where cedars, hemlocks and spruces
predominate, and in northern Maine is found in spruce woods, seemingly
because no other kinds are available."
Farther west, in northern Michigan, this warbler breeds on the open jack
pine plains and in mixed growths containing a fair percentage of other
conifers. Frank A. Pitelka (1940b) writes: "During the breeding season
the Black-throated Green Warbler is one of the more frequent
Compsothlypids in the conifer regions of northern lower Michigan, though
it is by no means to be included among the common birds. Locally it
occurs in spruces of mature bog communities and in upland developmental
forests of mixed pine and deciduous growth."
In western Pennsylvania, "its local breeding range is correlated rather
closely with the distribution of the white pine and the hemlock. Where
these conifers prevail, the Black-throated Green appears, although in
the mountains it is by no means averse to hardwood timber, if high and
dense" (Todd, 1940). And, in the Pymatuning Swamp region, "wherever tall
black birches and equally tall, slender hemlocks grew side by side, the
Black-throated Green Warblers were almost sure to be found, and no less
than twenty pairs were located" (Sutton, 1928). Referring to the central
Allegheny Mountain region, Prof. Maurice Brooks (1940) says that "this
species, in its distribution within our area, presents one of the most
puzzling problems with which we have to deal. It occurs everywhere at
high elevations, in spruce, hemlock, northern hardwoods, white pine,
oak-pine scrub, and oak-hickory."
Still farther south, on Mount Mitchell, in western North Carolina,
Thomas D. Burleigh (1941) found it to be "a plentiful breeding bird in
the thick fir and spruce woods at the top of the mountain, appearing in
April when the ground is frequently still covered with snow and
lingering in the fall until early October."
_Spring._--From its winter home in Mexico and Central America, the
black-throated green warbler, starting early in March, migrates
northward through eastern Texas and up the Mississippi Valley, mainly in
the forested areas. I noted it in the great wave of warblers migrating
along the Texas coastal islands early in May. The fact that it is so
rare in southern Florida, and still rarer in Cuba, suggests that many
individuals must make the perilous flight from Yucatan across the Gulf
of Mexico to the Gulf States. From Louisiana it takes a more
northeasterly route, mainly along the Alleghenies, to New England and
beyond. It is one of the earlier warblers to arrive in Massachusetts,
often during the last week in April. The birds come along in waves, the
first wave consisting mainly of males and later waves containing the
females in larger numbers. The passage of individuals seems to be fairly
rapid, but the species may be present for nearly a month at any point
along its migration route. While migrating it may be seen, like other
warblers, almost anywhere--in the tops of woodland trees, in roadside
trees and shrubbery, in gardens and in parks, before it settles down in
its favorite breeding haunts. There must be a very heavy migration
through Ohio, for Milton B. Trautman (1940) says that in the "larger
flight 50 to 125 were daily recorded, and it was evident that there were
several thousands present."
_Nesting._--Although the black-throated green warbler is one of our
commonest breeding warblers, I have never found its nest in my home
territory, though I have spent many hours hunting for it in its favorite
pine woods. While hunting through a somewhat open tract of pitch pines
on Martha's Vineyard, Mass., on June 8, 1919, with Frank C. Willard, we
found a nest with four fresh eggs 8 feet from the ground in a small
pine; it was saddled on an upward-slanting limb and partially supported
by a whorl of three small branches. It was a pretty nest, made of
grasses, seaweed, and strips of inner bark, and was lined with fine
grasses, cowhair, horsehair, and a few white feathers. The male was
incubating and was very tame, coming within a few feet of us; he also
returned and sat on the empty nest after Mr. Willard had removed the
eggs.
On June 4, 1910, Herbert K. Job showed me a nest near New Haven, Conn.,
in mixed deciduous woods; it was about 11 feet from the ground, built
against the trunk of a large chestnut sprout and supported by a small
dead branch and two live twigs; the leaves on this twig screened the
nest from above, one leaf forming a complete canopy over the nest, the
tip of it being tucked into the rim. It was made largely of materials
similar to those in the one previously described, there being three
large feathers on the rim and many small feathers in the lining.
The only other nest I have ever seen was found on the island of Grand
Manan, New Brunswick, on June 11, 1891; it was placed only 3 feet from
the ground between two horizontal branches and against the trunk of a
small spruce beside a cowpath in coniferous woods. It was a compact,
deeply hollowed, structure made of fine twigs, mosses, birch bark,
strips of inner bark, and weed stems, and it was lined with white
cowhair and a few feathers.
There is a set in my collection, given to me by Fred H. Carpenter, said
to have been taken from a nest only 8 inches from the ground in a small
red cedar in an old neglected pasture in Rehoboth, Mass. The nest, now
before me, seems to be typical of the species.
The nests mentioned in some notes sent to me by Miss Cordelia J.
Stanwood, of Ellsworth, Maine, were in spruces or hemlocks at low or
moderate heights, but Knight (1908) says that "near Bangor the species
builds fifty to seventy feet up in the larger, taller pine trees." Robie
W. Tufts tells me that, of some 20 or 30 nests that he has seen in Nova
Scotia, "all have been built in conifers, including hemlock, spruce, and
pine." In New York and Pennsylvania, hemlocks seem to be the favorite
nesting trees, but nests are sometimes placed in beeches or yellow
birches; the nests in hemlocks are usually placed on horizontal branches
at a considerable height from the ground and generally well hidden in
the foliage. A nest examined by Dr. George M. Sutton (1928) at
Pymatuning Swamp "was saddled on a horizontal bough only about
twenty-five feet from the ground, in a comparatively small hemlock. The
nest was very deep and beautifully constructed, its lining including
bits of hair, fur, and soft feathers, and its foundational material
consisting chiefly of slender and uniform twigs of dead hemlock."
The two nests studied by F. A. Pitelka (1940), in northern lower
Michigan, were on horizontal branches of Norway pines (_Pinus
resinosa_), 23 and 12 feet from the ground, respectively. The materials
used in the nests were largely similar to those mentioned above, with
the addition of woollike plant fibers and short pine twigs in the
lining, and with "a considerable quantity of hypnaceous mosses and bits
of birch bark" used as trimmings.
Dr. Paul Harrington writes to me: "I have found this bird nesting in
pure deciduous forests on two occasions." One nest was 40 feet up in the
crotch of an ironwood, and the other was 20 feet from the ground in a
small elm, both in Ontario. Edward R. Ford has sent me the following
note: "On Gull Island, about ten acres in extent, which lies in
northwestern Lake Michigan, we found the black-throated green warbler in
an unusual nesting niche. About half of the island's area is northern
hardwood forest, whose floor cover is largely of American yew (_Taxus
canadensis_). At a height of but two or three feet, among the sprays of
this ground-hemlock, we discovered two nests of the species named. Each
of these, July 12, 1918, held four eggs. There was a third nest, empty
but evidently used that season."
Nests have also been found in maples, in white, gray, and black birches,
in alders and probably in other deciduous trees and bushes. And the
following unusual nesting sites are of interest: William Brewster (1906)
mentions a nest that he found "in a barberry bush growing in an open
pasture at Arlington Heights, one hundred yards or more from the nearest
woods." He also has a nest, taken by C. H. Watrous in Connecticut, that
was on the ground "among a large clump of ferns in a very low and damp
place under a heavy growth of hemlocks" (Brewster, 1895). John C. Brown
(1889), of Portland, Maine, mentions a nest that was built in a
grapevine growing luxuriantly about a pagoda at some distance from any
woods; it was well hidden from the outside by the foliage, but in plain
sight from inside the pagoda. And B. S. Bowdish (1906) records a New
Jersey nest that "was built between the stems of a 'skunk cabbage'
plant, and fastened to a catbriar and the twigs of a dead bush, and was
about fourteen inches from the ground, in a very wet part of the swamp."
Miss Stanwood (1910) watched a pair of black-throated green warblers
building a nest in a fir tree, of which she writes:
First they laid knots of spider's silk and little curls of white birch
bark in the shape of the nest, on the horizontal fork about midway of a
branch six feet long. Next bits of fine grass, a little usnea moss, and
cedar bark fibre. Both the male and female worked on the nest, until
observed, the female shaping it with the breast each time they added a
bit of material. Around the top were carefully laid the finest gray
spruce twigs. These were bound together with masses of white spider's
silk. The white curls of birch bark, the much weathered twigs, the
fluffy shining bands and knots of spider's silk, made a very dainty
looking structure. After the first morning, I did not see the male about
the nest. As a general thing, I find that, if birds are observed
building, the male usually leaves his part of the work to the female.
The lady bird continued to shape the nest with her breast, turning
around and around, as if swinging on a central pivot, just her beak and
tail showing above the rim. If I came too near, she stood up in the nest
as if to fly. If I withdrew to a respectful distance, say three yards,
she went on with her work of shaping the nest. On the second day the rim
of the nest seemed about completed. It was narrower than the rest of the
cup and beautifully turned. Nothing to speak of had been done to the
bottom. On the fourth day, by touching the inside of the nest with the
tips of my fingers, I judged that the lining was about finished. It
consisted of rabbit-hair and horse-hair, felted or woven together so as
to be very thick and firm. Between the foundation of twigs and bark and
the hair lining was a layer of fine hay of which the mouth of the nest
was chiefly shaped. I never saw a more substantial looking little nest.
It was also one of the most beautiful I have ever found, a perfect
harmony in grays.
A very pretty nest in my collection is largely made, externally, of
usnea and is profusely decorated with masses of the curly outer bark of
the yellow birch. The larger of two nests before me measures about 4 by
3-1/2 inches in outer diameter, the smaller about 3 inches; both are
about 2 inches high, nearly 2 inches wide and 1-1/2 deep inside.
_Eggs._--The black-throated green warbler usually lays 4 eggs to a set,
but quite often 5. These are ovate to short ovate and slightly glossy.
The ground color is grayish white or creamy white. The markings consist
of specks, spots, blotches, or small scrawls of reddish browns, such as
"auburn," "chestnut," "bay," "Mars brown," or "russet," with underlying
spots of "light brownish drab," "deep brownish drab," or "light purplish
drab." Generally the markings are concentrated at the larger end, where
they usually form a wreath, but occasionally the spots are well
scattered over the entire egg. There is considerable variation. Some
eggs have a faint wreath of the pale drab coloring which is relieved
with a few bold spots or scrawls of dark "bay" or "Mars brown." Others
are richly spotted and blotched equally with browns and drabs, or they
may have a solid ring of "russet" blotches which completely covers and
conceals the drab undertones. The measurements of 50 eggs average 17.0
by 12.7 millimeters; the eggs showing the four extremes measure =18.8=
by 12.8, 17.2, by =13.4=, =15.5= by 12.2, and 18.0 by =12.0= millimeters
(Harris).
_Young._--It is generally conceded that the period of incubation is
about 12 days and that the young remain in the nest from 8 to 10 days,
depending on the amount of disturbance. Probably the female does most,
or all, of the incubating and brooding, but both sexes assist in feeding
the young and in swallowing or removing the fecal sacs. Miss Stanwood
(1910b) refers to the development of the young as follows: "On the third
day the young birds grow rapidly, burnt-orange in color, covered with an
abundant supply of burnt-umber down. The quills and pin feathers showed
blue-gray through the skin, and the eyes were just beginning to open."
At another nest, "on the eighth day, the nest was simply stuffed full of
little green-gray birds, strikingly like the color of the nest.
* * * On the eleventh day, quite early in the morning, as I neared the
nesting place, I heard the fledglings calling from the tree-tops. Soon I
caught a glimpse of the Black-throated Green Warblers marshalling their
little band away."
Margaret M. and L. B. Nice (1932) made detailed studies of two nests of
this warbler, to which the reader is referred. I quote from their
summary:
1. The young in the first nest were raised with no assistance from the
male until the last two days, when he brought 11 meals in contrast to
his mate's total of more than 245. The young in the second nest were
raised entirely by the female. 2. The first female incubated for periods
ranging from 34 to 50 minutes, absenting herself for periods ranging
from 9 to 26 minutes. The second female once incubated for 99 minutes at
a stretch; her absences varied from 13 to 20 minutes. 3. Both females
brooded for longer periods than the majority of arboreal Warblers that
have been studied, averaging 15.1 and 18.3 minutes respectively. 4. Both
females fed at slow rates, the average for the first being once in 19.7
minutes, for the second once in 16.3 minutes. * * * (6). Both females
made definite efforts to get their last young out of the nest and to
lead them to a distance.
Pitelka (1940b) gives many interesting details on the home life of the
black-throated green warbler, illustrated with charts and tables that
are not suitable for inclusion here, but his paper is well worth careful
study.
Reading and Hayes (1933) made some intimate studies of these warblers at
their nest; referring to the food of the young, they say: "Observations
at less than two feet revealed the tremendous value of these birds as
insect destroyers. Spiders, may-flies, green caterpillars (Anisota),
ants, small noctuid moths, ichneumon flies, crane flies, and many
smaller diptera made up the whole of their menu. While the few spiders
and ichneumon flies were harmless or possibly beneficial, many of the
other insects were injurious."
_Plumages._--Dr. Dwight (1900) calls the natal down sepia-brown and
describes the juvenal plumage, in which the sexes are alike, as "above,
sepia-brown or drab. Wings and tail dull black, edged with ashy or
olive-gray; two wing bands white; the outer three rectrices largely
white. Below, dull white, dusky on the throat, spotted on the breast and
sides with dull olive-brown. Indistinct grayish white superciliary line.
Dusky transocular streak."
A partial postjuvenal molt, beginning in July and involving the contour
plumage and the wing coverts but not the rest of the wings or the
tail, produces the first winter plumage, in which the sexes are
distinguishable. He describes the young male as--
above, greenish olive-yellow, the upper tail coverts ashy or plumbeous
gray edged with olive yellow. The feathers of the crown and back
especially have concealed black shaft streaks. The wing coverts are
black, edged with olive green; two broad white wing bands tipped faintly
with yellow. Below, faint primrose-yellow, white on the crissum; the
breast and a spot on the flanks canary, the chin, sides of head and neck
and superciliary line bright lemon-yellow; a variable area on the throat
seldom including the chin, black, veiled by long narrow edgings, the
sides and flanks broadly streaked and similarly veiled. Transocular and
rictal streaks dusky; lores grayish. * * * In first winter plumage the
female is browner than the male, without the black throat and the side
streaks obscure; some specimens with much black may, however, easily be
mistaken for dull first winter males.
The first nuptial plumage is acquired by a partial prenuptial molt,
"which involves chiefly the head, chin and throat and not the rest of
the plumage. The black chin is assumed by the male and the forehead
becomes yellower by moult, wear removing the edgings everywhere so that
the streakings below and the throat become jet-black. Young and old
become practically indistinguishable, except that the wings and tail of
the young bird will average browner and more worn with the edgings
duller." In the female, "the first nuptial plumage differs very little
from the first winter, wear bringing out the streaking, while a few
feathers are assumed by moult on the chin."
A complete postnuptial molt occurs in July, producing the adult winter
plumage, in which the male "differs somewhat from the first winter, the
black of the throat extending uninterruptedly to the apex of the chin,
further down on the throat, and in broader stripes on the sides; the
wings and tail are blacker and the edgings grayer, especially on the
tertiaries; the concealed black of the back more extensive. The veiling
is conspicuous on the throat." The adult winter female is much like the
first winter male, "and may have considerable black on the throat, and
even the chin."
The adult nuptial plumage is acquired mainly by wear, with only slight
indications of molt, as in the young bird. Dr. Dwight says of the
female: "The adult nuptial plumage is, in extreme examples, hardly
distinguishable from the male, but usually the black is much restricted
and the chin yellow, merely spotted with black."
_Food._--We have only scattering reports on the food of the
black-throated green warbler. S. A. Forbes (1883) examined the stomach
of one taken in an orchard infested with canker-worms in Illinois, and
found it to contain 70 percent of these destructive caterpillars, 15
percent beetles, 5 percent Hemiptera, and the remaining 10 percent
Hymenoptera, gnats, coleopterous larvae and mites. Five stomachs of
Nebraska birds, collected by Professor Aughey (1878), contained an
average of 23 locusts and 21 other insects. Of twelve specimens examined
by F. H. King (1883) in Wisconsin, "one had eaten a moth; three, seven
caterpillars; one, two diptera; one, six larvae--probably caterpillars;
three, eleven beetles; and one, a heteroptera."
Knight (1908) from Maine writes: "The food consists almost entirely of
insects, including beetles, flies, moths, spiders, grubs, larvae and in
general the sorts of insects found on the limbs and foliage of the
various evergreen trees and especially on the pines. Only rarely do they
take their prey in the air, preferring to diligently seek it out among
the branches and foliage."
Probably all the items mentioned in the food of the young are also eaten
by the adults. Forbush (1929) adds to the list leaf rollers,
leaf-eating caterpillars of various kinds, and plant-lice. Evidently
these warblers are among the best protectors of our forest trees. W. B.
Barrows (1912) says that they are "particularly fond of the berries of
the poison-ivy, and to a less extent of those of the junipers." J. K.
Terres (1940) saw them tearing open the nests of tent caterpillars,
devouring large quantities of the larvae, which were about
three-quarters of an inch long.
_Behavior._--Although the black-throated green warbler is one of our
tamest and most confiding wood warblers, as shown by the intimate
studies of its home life made by several observers, it is much more
often heard than seen, for it is a tiny mite and spends most of its time
in the tree-tops, gleaning in the foliage of both coniferous and
deciduous trees. As Miss Stanwood (1910b) says: "The bird is quick in
its movements, but often spends periods of some length on one tree,
frequently coming down low to peep inquisitively at an observer, once in
a while flying toward a person as if to alight on his hand or head."
Forbush (1929) draws a picture of its confidence: "Like all the wood
warblers it is fond of bathing, its bath tub often some pool in a
mountain trout brook. One day as I stood beside such a brook, a very
lovely male, disregarding my presence, alighted on a stone at my feet,
and at once hopped into the clear spring water and performed his
ablutions, dipping into the stream and throwing off the sparkling drops
in little showers. As he stood there in the sunlight which streamed
through an opening in the tree-tops, he left an enduring picture in my
memory."
Those who have studied the home life of the black-throated green warbler
have noted its intolerance of some avian intruders in the vicinity of
its nest, and its tolerance of others. Pitelka (1940b) writes: