late February and is not finished before about the middle of March. The
molt involves most of the anterior body plumage, but progresses so
slowly that this species never has the ragged 'pin-feathered' appearance
so often seen in _Dendroica aestiva_ at the spring molt." Dr. Dwight
noticed the beginning of this molt as early as January 14. He says it
"involves chiefly the head, chin and throat. The ashy gray cap is
acquired, the chin, throat, and superciliary line become white, the
throat is tinged with cream-buff and the transocular streak black. The
yellow tints of the feathers retained below are lost by wear." In the
female, this molt is less extensive than in the male, and "the crown
never becomes, even in later plumages, as gray as that of the male, but
always has a brown or greenish tinge."
Subsequent molts consist of a complete postnuptial in July and a partial
prenuptial molt in late winter and early spring as in the young bird.
_Food._--Bowdish and Philipp (1916) sent four stomachs of birds
collected in June to the U. S. Biological Survey for analysis. One of
these was empty. Of the other three, one contained 8 small caterpillars
(Tortricidae), 35 percent; dipterous fragments, 23 percent; a small
spider, 2 percent; and scalelike fragments (perhaps of some catkin), 40
percent. Another held a camponotid ant, 16 percent; at least 78 small
caterpillars (Tortricidae), 75 percent; a snail (_Vitrea hammoides_), 4
percent; and unidentified vegetable fragments, 5 percent. The other
contained 3 lampyrids (near _Podabrus_), 8 percent; a small coleopterous
(?) larva, 3 percent; about 15 small caterpillars (as above), 25
percent; a neuropterous insect (apparently a caddis fly), 50 percent; 2
small spiders, 14 percent; and a trace of unidentified vegetable matter.
Several observers have complained that Tennessee warblers do
considerable damage to grapes, and this is undoubtedly true. W. L.
McAtee (1904), while investigating the damage done by this and the Cape
May warbler, found that--
in the arbor under observation, which was a small one, scarcely a grape
and not a cluster was missed. The damage, however, was inconsiderable as
the birds did not commence to use their appropriated share of the crop
until the owner had taken all he desired. * * * Both species were
constantly busy catching insects on the vines, and on a walnut and some
appletrees near by. Frequently, however, they dashed into the vines and
thrust their bills quickly into a grape. Sometimes they withdrew them
quickly; again they poked around in the interior of the grape a little,
and always after these attacks, they lifted their heads as in drinking.
This action suggested a reason for piercing the grapes, that I am
satisfied is the true one, that is, the obtaining of liquid refreshment.
A supply of available drinking water for the birds, might help to
protect the grapes. And, as the warblers feed on insects that seriously
damage the grapevines, the good work they do may compensate for the
grapes that they damage. The stomach of one Tennessee warbler examined
by Mr. McAtee contained a _Typhlocyba comes_, an especial pest of the
grape, a destructive jassid or leafhopper, 6 caterpillars which were
doing all in their power to eat up the leaves remaining on the vines, 2
spiders, a bug (_Corizus_), a weevil, and one parasitic hymenopteron
(the only insect that was not harmful).
S. A. Forbes (1883) found that a stomach taken from an orchard infested
by canker-worms contained about 80 percent of these destructive larvae
and about 20 per cent beetles. Professor Aughey (1878) observed these
warblers catching young locusts in Nebraska. Clarence F. Smith adds, in
some notes sent to me, that "in the fall, during migration time,
Tennessee warblers often glean their food from dense patches of such
weeds as sunflower, goldenrod, and ragweed," and that "sumac, poison
ivy, and other berries are sometimes eaten in small quantity."
F. H. King (1883) has considerable to say about the damage done to
Delaware and Catawba grapes in Wisconsin; as soon as they are wounded,
they are attacked by ants, bees, and flies and soon destroyed. But he
thinks the service rendered more than compensates for the harm done. He
refers to the feeding habits of the Tennessee warbler as follows:
It is very dexterous in its movements, and obtains the greater part of
its food upon and among the terminal foliage of trees. Titmouse-like, it
often swings pendant from a leaf while it secures an insect which it has
discovered. Small insects of various kinds, not especially attractive to
larger birds, are destroyed by this species in large numbers; and its
slender, acute bill serves it much better in picking up these forms than
a heavier, more clumsy one could. * * * Of thirty-three specimens
examined, two had eaten two very small hymenoptera (probably parasitic);
seven, thirteen caterpillars; three, fifteen diptera; six, thirteen
beetles; three, forty-two plant-lice, among which were two specimens of
the corn plant-louse _Aphis maidis_ (?); three, thirty-five small
heteroptera, .09 of an inch long; and one, eleven insect eggs.
Alexander F. Skutch has sent me the following interesting notes on the
feeding habits of the Tennessee warbler in Central America: "I was
surprised to find last month [March] that these warblers were visiting
my feeding shelf on the guava tree in the yard. About the only food I
ever serve to the birds on this table is bananas and occasionally
plantains; and my chief guests are tanagers of about half a dozen
brilliant kinds, a few finches, honeycreepers, and wintering Baltimore
orioles. But the Tennessee warblers soon formed the habit of visiting
the table and sharing the food with the bigger resident birds.
"Some seemed to linger in the vicinity much of the day, making frequent
visits to the board and each time eating liberal portions of banana or
the somewhat harder ripe plantain. They were intolerant of each other,
and one individual would not let a second alight on the board until it
had finished its own meal, although there was plenty of room and plenty
of food for all. I have noticed also that the Tennessee warblers chase
each other as they forage among the trees in wintering flocks. I cannot
recall ever having seen any other wood warbler eat banana.
"Last November 14 a Tennessee warbler behaved most surprisingly. The
grass in the yard had grown very long, and I had it cut with a machette.
Late in the afternoon, after the usual rain, a lone Tennessee warbler
flew down on the fallen grass and began to hop over it, catching small
insects.
"It also entered the uncut grass, about a foot high, and disappeared
momentarily amidst it. Twice driven up by passing people, each time it
promptly returned to the grass. Its third visit to the cut grass was
longest. While I stood quietly watching, it hopped deliberately about,
much in the manner of a house wren, and gathered an abundant harvest
from the fallen herbage. Once it found a caterpillar about an inch long,
which it carefully bruised in its mandibles before swallowing it. The
warbler was amazingly bold, and hopped over the grass within a yard of
my feet, and allowed me to follow closely as it moved away. Early the
following morning, and again at the close of the day, the warbler
foraged over the lawn in the same fashion. In the evening, it continued
to creep slowly over the mown grass and after all other birds had
disappeared into their roosts, and the light was becoming too dim to see
it clearly."
_Behavior._--Much of the behavior of the Tennessee warbler has been
mentioned above, and there is little more to be said. It is a very close
sitter on its nest, when incubating, and has been caught there by
throwing a hat or a net over it; but, when flushed, it is rather shy
about returning to it, usually making its demonstrations of protest by
flitting about at a safe distance and nervously uttering a sharp _chip_.
The Prebles (1908) witnessed a rather remarkable flight behavior at Fort
Resolution, Mackenzie:
During the forenoon of June 25, an extremely windy day, we observed a
remarkable movement of these warblers. They came from the northward,
flying over the point of land on which the fort is built In loose flocks
of from 10 to 20 individuals. After passing the point, they either
struck out directly across the bay or skirted the shore, in either case
having to face a strong southeast wind. Some paused a few moments among
the low bushes on the point, but the slightest alarm started them off.
The flight lasted over two hours, and, during this time, upward of 300
birds were seen from our camp. Two specimens, a male and a female, were
collected. The ovaries of the female contained eggs only slightly
developed.
_Voice._--Aretas A. Saunders contributes the following: "The song of the
Tennessee warbler is a rapid series of short, loud, unmusical notes. It
has been compared to the song of the chipping sparrow, but it varies
more in pitch, time, and loudness, and is distinctly in two or three
parts. To my ear it is much more like the chippering of a chimney swift.
"In 35 records of this song, the number of notes varies from 9 to 25,
the average being 17. Only one song has a true trill in it, that is,
notes so rapid that they cannot be counted. Each song is of either two
or three parts, each part composed of a series of notes on the same
pitch and in uniform rhythm. The parts differ from each other in pitch,
time, or loudness. In a number of songs, one of the parts is a
repetition of 2-note phrases. Loudness generally increases to the end of
the song, but sometimes the reverse is true. Some songs rise in pitch to
the end and others fall; my records are about evenly divided in this
matter. A typical three part song would be something like
_tit it it it it it it pita pita pita pita pita
chit chit chit chit chit_.
"Pitch varies from G´´´ to E´´´´, or four and a half tones. Single songs
vary from half a tone to three and a half tones, averaging one and a
half. The length of songs varies from 1-4/5 to 3-1/5 seconds. An
individual bird may sing a dozen different variations of the song in a
short time. On the other hand, I have heard three birds in one tree
singing alternately, the songs of all three being exactly alike so far
as my ear could determine."
Francis H. Allen gives me his impression of the song as follows: "The
song bears some resemblance to that of the Nashville warbler, but is
easily distinguished. I have written it
_wi-chip wi-chip wi-chip wi-chip, wi-chip wi-chip
chip chip chip chip chip chip chip_.
The higher notes in the middle sometimes appear to be monosyllables, and
they are sometimes omitted. The series of _chips_ at the end are very
emphatic, and the last one is perhaps accented somewhat. All the notes
are staccato."
Various other renderings of the song have appeared in print, but they
all give the same impression of a variable, loud, striking song which,
once learned, can be easily recognized. The bird is a very persistent
singer rivaling the red-eyed vireo in this respect. Bowdish and Philipp
(1916) write: "As a basis for estimating the frequency of song
repetition, counts were kept on three singing birds for a period of 5
minutes each, with a result of 32, 36, and 22 songs, respectively,
within the period. In one instance, a bird was observed to sing while on
the wing, repeating the song twice in the course of a short flight."
Albert K. Brand (1938) found the pitch of the Tennessee warbler's song
to be well above the average, the approximate mean count being 6,600
vibrations per second, the highest note about 9,150 and the lowest
4,025; this compares with an approximate mean of 8,900 vibrations per
second for the black-poll warbler, and about 4,000 for the average
passerine song.
_Field marks._--The Tennessee warbler has no prominent wing-bars and no
very conspicuous field marks. It might be mistaken for one of the small
vireos, but its bill is much more slender and acute. The male has a gray
crown, a light line over the eye, and a dusky line through it; the upper
parts are bright olive-green and the under parts grayish white. The
female has a greener crown and more yellowish under parts. For more
details, see the descriptions of plumages.
_Fall._--The fall migration starts early in August, but is quite
prolonged, many birds lingering in the northern States until early in
October and in the southern States all through that month. During some
seasons and at certain places the Tennessee warbler is exceedingly
abundant, sometimes far outnumbering any other species, but it is very
variable in its abundance.
Mr. Trautman (1940) says that at Buckeye Lake, Ohio, "during some years
not more than 20 individuals could be recorded in a day in the southward
migration, nor more than a 100 in the season. In other years the bird
rivaled the Myrtle Warbler in numbers, and as many as 1,000 individuals
could be seen in a day and several thousands during a migration. * * *
Throughout the southward migration the species did not confine itself to
the upper sections of the taller trees as in spring, but was found in
almost equal numbers in smaller trees and brushy thickets, in bushes and
saplings along fence rows, and in weedy fields."
Professor Cooke (1904) says of the fall migration route: "The principal
line of migration is from the Mississippi Valley across the Gulf of
Mexico to Mexico and Central America. The eastern part of this route
probably extends from the southern end of the Alleghenies across
northwestern Florida to the coast of Yucatan and Honduras." A. H. Howell
(1932), however, gives several records for central and southern Florida,
and says: "In autumn, Weston reports a large migration on October 26 and
27, 1925, when 31 birds were killed at the lighthouse near Pensacola on
the two nights, and large numbers seen on the morning of October 26 in
vacant lots in the city."
Dickey and van Rossem (1938) say of the migration in El Salvador:
During the fall migration of 1925, Tennessee warblers arrived in the
vicinity of Divisadero on October 13. No advance guard, that is,
individuals arriving ahead of the main flights, was observed in this
case. On the above-mentioned date they were suddenly found to be present
in numbers, and from then on were common in every lowland or foothill
locality visited. In point of relative abundance this was by far the
most common warbler (resident or migratory) throughout the coastal plain
and in the foothills, but it was greatly outnumbered by _Dendroica
virens_ above 3,000 feet.
The manner of occurrence was usually as small flocks of six or eight or
even twenty or more birds. These combined with several other species to
make up larger flocks which worked ceaselessly through the crown foliage
of low, semi-open woodland. However, many were found even in the tall,
dense swamp forests along the coast and also in the oak woods on Mt.
Cacaguatique.
_Winter._--Dr. A. F. Skutch has contributed the following account: "The
Tennessee warbler winters in Central America in vast numbers. Coming
later than many other members of the family, the first individuals
appear in mid-September; but the species is not abundant or widely
distributed until October. During the year I passed on the Sierra de
Tecpán in west-central Guatemala a single Tennessee warbler appeared in
the garden of the house, at 8,500 feet, on November 7 and despite frosty
nights lingered into December. On November 19, 1935, I saw one on the
Volcán Irazú in Costa Rica at 9,200 feet--the highest point at which I
have a record of the species. At the other extreme I found a few of
these adaptable birds among the low trees on the arid coast of El
Salvador in February and among the royal palms at Puerto Limón, on the
humid coast of Costa Rica, in March. But Tennessee warblers are most
abundant as winter residents at intermediate altitudes, chiefly between
2,000 and 6,000 feet above sea-level. From 3,000 to 5,000 feet they
often seem to be the most abundant of all birds during the period of
their sojourn. They travel in straggling flocks and form the nucleus of
many of the mixed companies of small, arboreal birds. At times 'myriads'
is the only term that seems apt to describe their multitudes.
"I think 'coffee warbler' would be a name far more appropriate than
Tennessee warbler for this plainly attired little bird; it was merely a
matter of chance that Alexander Wilson happened to discover the species
in Tennessee rather than at some other point on its long route from
Canada to Central America; but the warblers themselves manifest a
distinct partiality to the coffee plantations. The open groves formed by
the shade trees, whose crowns rarely touch each other, yet are never far
apart, seem to afford just the degree of woodland density that they
prefer. It matters not whether these trees are Grevilleas from Australia
with finely divided foliage, or Ingas with large, coarse, compound
leaves, or remnants of the original forest--a mixture of many kinds of
trees with many types of foliage: from Guatemala to Costa Rica the
Tennessee warblers swarm in the coffee plantations during the months of
the northern winter and are often the most numerous birds of any species
among the shade trees. Possibly they may at certain times and places be
as multitudinous in the high forest as in the plantations. Although I
have never found them so, the negative evidence must not be allowed to
weigh too heavily, for such small, inconspicuous birds, devoid of bold
recognition marks, are not easy to recognize among the tops of trees
over a hundred feet high.
"Tennessee warblers are fond of flowers, especially the clustered heads
of small florets of the Compositae and Mimosaceae, and of the introduced
Grevillea that sometimes shades the coffee plantations. They probe the
crowded flower clusters, perhaps seeking small insects lurking there
rather than nectar. The white, clustered stamens of the Inga--the most
generally used shade tree of the coffee plantations--are especially
attractive to them. Local movements within their winter range appear to
be controlled by the seasonal abundance of flowers. So, in the valley of
the Río Buena Vista in southern Costa Rica, at an altitude of about
3,000 feet, I found Tennessee warblers very abundant during December and
January. Here they flocked not only in the forest and among the shade
trees of the little coffee groves, but also in great numbers through the
second-growth thickets that filled so much of the valley, where at this
season there was a profusion of bushy composites with yellow or white
flower-heads, and of acacia-like shrubs (_Calliandra portoricensis_)
with long, clustered, white stamens. But during February, the third dry
month, the thickets became parched and flowered far more sparingly. Now
the Tennessee warblers rapidly declined in numbers, and before the end
of the month disappeared from the valley. During the following year,
which in its early quarter was far wetter, a number remained through
March, and a few well into April.
"Tennessee warblers pluck the tiny, white protein corpuscles from the
brown, velvety bases of the long petioles of the great-leafed Cecropia
trees, taking advantage of these dainty and apparently nutritious
tid-bits when the usual Azteca ants fail to colonize the hollow stems;
for only on trees free of ants does this ant-food accumulate in
abundance.
"While the Tennessee warbler departs during February from some districts
where it is common in midwinter, it remains until April in regions where
the dry season is not severe. After the middle of April it is only
rarely seen in Central America; and there appears to be no record of its
occurrence in May."
DISTRIBUTION
_Range._--Canada to northern South America.
_Breeding range._--The Tennessee warbler breeds =north= to southwestern
Yukon (Burwash Landing and the Dezadiash River); southern Mackenzie
(Mackenzie River below Fort Wrigley, lower Grandin River, and Pike's
Portage); northeastern Manitoba (Churchill and York Factory); central
Quebec (Fort George, Lake Mistassini, and Mingan); and possibly southern
Labrador (Hawkes Bay). =East= to southeastern Labrador (Hawkes Bay);
central Newfoundland (Lamond and Gaff Topsail). =South= to central
Newfoundland (Gaff Topsail); Nova Scotia (Wolfville); southern New
Brunswick (Grand Manan); northern and central western Maine (Mount
Katahdin, Livermore, and Lake Umbagog); north-central New Hampshire
(Mount Washington); south-central Vermont (Rutland); possibly
northwestern Massachusetts (Hancock); southern New York (Slide
Mountain); southern Ontario (Ottawa, North Bay, and Biscotasing;
probably occasionally farther south); west-central Michigan (Duck Lane);
probably northern Wisconsin (Plum Lake); northern Minnesota (Tower, Cass
Lake, and Warren); southwestern Manitoba (Margaret and Aweme); central
Saskatchewan (Emma Lake; has been found in the breeding season at Indian
Head, Old Wives Creek, and Maple Creek); southern Alberta (Flagstaff,
Red Deer, and Banff); and south-central British Columbia (150 Mile House
and Kimquit). =West= to western British Columbia (Kimquit, Hazelton,
Telegraph Creek, and Atlin); and southwestern Yukon (Dezadiash River and
Burwash Landing).
_Winter range._--In winter the Tennessee warbler is found =north= to
central Guatemala (Volcán de Santa María, Cobán, and Gualán).
=East= to eastern Guatemala (Gualán); northeastern El Salvador
(Mount Cacaguatique); eastern Nicaragua (Río Escondido); eastern Costa
Rica (Puerto Limón); eastern Panamá (Barro Colorado and Permé); northern
Colombia (Santa Marta region); and northern Venezuela (Caracas). =South=
to northern Venezuela (Caracas and Mérida); and northwestern Colombia
(Concordia). =West= to western Colombia (Concordia and Antioquia);
Panamá (Paracaté); Costa Rica (El General and Liberia); El Salvador
(Puerto de Triunfo); and Guatemala (Tecpán and Volcán de Santa María).
It has also been found to the first of January (possibly delayed
migration) at Knoxville (1936) and at Nashville (1935), Tenn.; and one
wintered (1934-35) in Cameron County, Tex.
_Migration._--Late dates of departure from the winter home are:
Colombia--Miraflores, April 19. Costa Rica--San Isidro del General,
April 30. El Salvador--San Salvador, April 25. Guatemala--Livingston,
April 8. Chiapas--Tixtla Gutiérrez, May 8. Tamaulipas--Gómez Farías,
April 27.
Early dates of spring arrival are: Cuba--Habana, April 8.
Florida--Sandy Key, April 13. Georgia--Athens, April 13. District of
Columbia--Washington, May 2. West Virginia--French Creek, April 20.
Pennsylvania--McKeesport, April 27. New York--Corning, May 3.
Massachusetts--Northampton, May 8. Maine--Waterville, May 11. New
Brunswick--Petitcodiac, May 19. Quebec--Quebec, May 19. Louisiana--Avery
Island, April 6. Arkansas--Winslow, April 8. Tennessee--Memphis, April
9. Kentucky--Bowling Green, April 19. Indiana--Bloomington, April 12.
Ohio--Columbus, April 25. Michigan--Ann Arbor, April 21.
Ontario--Ottawa, May 12. Missouri--Columbia, April 22. Iowa--Sigourney,
April 25. Wisconsin--St. Croix Falls, April 25. Minnesota--Clarissa,
April 30. Kansas--Winfield, April 19. Nebraska--Red Cloud, April 18.
South Dakota--Vermillion, May 1. North Dakota--Fargo, May 1.
Manitoba--Margaret, May 3. Colorado--Estes Park, May 14.
Wyoming--Torrington, May 12. Montana--Great Falls, May 9.
Alberta--Belvedere, May 1. British Columbia--Carpenter Mountain,
Cariboo, May 15; Atlin, May 26.
Late dates of spring departure of transients are: Cuba--Habana, May 5.
Florida--Fort Myers, May 15. Alabama--Melville, May 3. Georgia--Athens,
May 7. North Carolina--Chapel Hill, May 3. Virginia--Falls Church, June
3. District of Columbia--Washington, June 3. Pennsylvania--Warren, May
30. New York--Rochester, June 6. Massachusetts--Beverly, June 3.
Vermont--Wells River, June 5. Louisiana--Shreveport, May 15.
Mississippi--Oxford, May 15. Arkansas--Delight, May 20.
Tennessee--Nashville, May 21. Illinois--Lake Forest, June 3.
Ohio--Toledo, June 5. Michigan--Houghton, June 7. Ontario--Toronto,
June 7. Missouri--Columbia, May 31. Iowa--Sioux City, June 6.
Wisconsin--Racine, June 4. Minnesota--St. Paul, June 1.
Kansas--Lawrence, May 24. Nebraska--Omaha, May 28. South
Dakota--Faulkton, June 5.