While the Chestnut-sided Warbler breeds mostly in the northeastern potion of the U.S. and southeastern Canada, it has occurred as a vagrant in every U.S. state except Hawaii. The Chestnut-sided Warbler’s preference for forest habitat in an early successional stage enabled it to expand its range with forest clearing in the late 1800s.
Chestnut-sided Warbler males have two types of songs. The first is used to establish and defend a territory early in the breeding season, while the second type is used to square off with rival males later in the nesting season.
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Description of the Chestnut-sided Warbler
The Chestnut-sided Warbler in breeding plumage has blackish upperparts striped with white, a yellow crown, a black frame around white cheeks, yellowish wing bars on dark wings, and chestnut red along the sides just below the wings
Males have a bolder black face frame. Length: 5 in. Wingspan: 8 in.
Females have a paler face frame.
Seasonal change in appearance
Fall males and females have greenish upperparts, a white eye ring, and lack the black face frame, making them look much different than breeding birds.
Immatures are similar to fall adults, but lack the chestnut sides.
Chestnut-sided Warblers inhabit overgrown pastures and woodland edges with brush.
Chestnut-sided Warblers eat insects.
Chestnut-sided Warblers forage actively in shrubs and small trees, gleaning prey from leaves and twigs.
Chestnut-sided Warblers breed in southern Canada, the northeastern U.S., the Great Lakes Region, and the Appalachians. They winter from Mexico to Central America. The population has declined in recent decades.
Bent Life History
Visit the Bent Life History for extensive additional information on the Chestnut-sided Warbler.
Forest clearing in the 1800s led to a significant population expansion of this brush specialist. Reforestation means less habitat is available today.
Chestnut-sided Warblers are often quite tame, and allow a close approach.
The song is a musical series of “witchew witchew witchew” notes. A buzzy flight call is also given.
Attracted by water features.
Bay-breasted Warblers lack the pale face, and have white wing bars.
The Chestnut-sided Warbler’s nest is a cup of bark strips, grasses, and roots lined with finer materials. It is placed in a dense shrub or vine tangle.
Number: Usually lay 4 eggs.
Color: Whitish with darker markings.
Incubation and fledging:
The young hatch at about 11-12 days and fledge at about 10-12 days, though remaining dependent on the adults for some time.
Bent Life History of the Chestnut-sided Warbler
Published by the Smithsonian Institution between the 1920s and the 1950s, the Bent life history series of monographs provide an often colorful description of the birds of North America. Arthur Cleveland Bent was the lead author for the series. The Bent series is a great resource and often includes quotes from early American Ornithologists, including Audubon, Townsend, Wilson, Sutton and many others.
Bent Life History for the Chestnut-sided Warbler – the common name and sub-species reflect the nomenclature in use at the time the description was written.
DENDROICA PENSYLVANICA (Linnaeus)
Many changes have taken place in the distribution and relative abundance of many birds in different parts of our land since the settlement of the country, owing to the changes wrought in the landscape by man. The beautiful little chestnut-sided warbler is one of the species that has benefited, flourished, and increased with the spread of civilization. It seems strange that such a common, well-marked, and familiar species, as we now know it to be over so much of northeastern North America, should have been largely unknown by the early writers on American birds. Edward H. Forbush (1929) tells the story very well as follows:
Audubon met with it but once; Wilson saw little of it; Nuttall, who considered it rare, evidently knew little about it, and saw very few. Since his time, however, its numbers have increased until it has become one of the commonest of eastern warblers. Its increase was favored by the destruction of the primeval forest and the continued cutting away of subsequent growths, and later by the increase of neglected fields and pastures with their growths of bushes and brambles, for it is not a frequenter of deep woods, nor yet of well-kept gardens, orchards or farmyards, but prefers neglected or cut-over lands, with a profusion of thickets and briers. So we may find It usually away from houses, In low roadside and brookside thickets, or in sproutlands rather recently cut over. As the coppice grows up the bird retires to other quarters or to the edges of the woods.
According to William Brewster (1906), the chestnut-sided warbler began to appear in the Cambridge region in about 1830 or 1831, when Nuttall began to find it, but he writes: “Dr. Samuel Cabot told me a year or two before his death that when he was at Harvard College (1832: 1836) the Chestnut-sided Warbler was certainly very rare in eastern Massachusetts, and that for some years later it was not common although it gradually but steadily increased in numbers after 1835.” A similar increase in numbers has been noted in other places. Dr. Chapman (1907) says: “In my own experience, covering the past twenty-five years, at Englewood, N. J., I have seen this Warbler become established as an increasingly common summer resident.” And A. Radclyffe Dugmore (1902) writes, in reference to the same general legion: “In the summer of 1897, the first year that I did any systematic bird work in this locality, these birds were so little in evidence that I did not observe a single specimen.” During the next two years a few pairs were discovered in suitable clearings, but “in 1900 the Warblers were comparatively common, every clearing containing several pairs, and last summer they were still more abundant, four pairs occupying a clearing of only a few acres, while in the large clearing there were more than could be counted with accuracy; probably not less than seven or eight pairs.~~ The breeding range of the chestnut-sided warbler is now known to extend from central Saskatchewan and Newfoundland on the north throughout southern Canada and the northern half of the United States east of the great plains; but it is much commoner in the States than in Canada, and its breeding range extends farther south in the Alleghenies, to northern Georgia. Writing of the birds of the central Allegheny Mountains, Prof. Maurice Brooks (1940) calls it “one of the most abundant warblers in mountainous cut-over areas. It is a characteristic bird of the ‘chestnut sprout’ association, and reaches the edges of the spruce forests. In northern West Virginia it breeds down to 1200 feet, and it occurs up to 4800 feet where the habitat is suitable. Mountain laurel thickets offer a favorite nesting place, and dead chestnut trees are often used as singing places.” Referring to northeastern Georgia, Thomas D. Burleigh (1927a) writes: “I have noted a few singing males as low as 3500 feet, but it is only above an elevation of 4000 feet that these birds occur in any numbers. Within a few hundred yards of the top of Brasstown Bald the south slope is covered with small stunted oaks that are few enough in number to encourage a thick undergrowth of laurel and huckleberry bushes. In this limited area the Chestnut-sided Warblers are actually plentiful, and are among the few birds that can be found breeding there.
Spring: According to Dr. Chapman (1907), “the Chestnut-sided Warbler passes through eastern Mexico and the Gulf States from northwestern Florida to eastern Texas. It is casual in southern Florida and the Bahamas.”
M. A. Frazar (1881) saw “quite a number” migrating across the Gulf of Mexico, when his ship was about 30 miles south of the Mississippi delta. In the great wave of migrating warblers and other small birds that I saw on the islands in Galveston Bay, Texas, on May 4, 1923, chestnut-sided warblers were much in evidence, as they generally are in all of these transient hosts; here they were buffeted about by a northerly gale and were seeking shelter behind every little eminence or clump of bushes, to rest before struggling again against the wind.
The spring migration along the eastern route seems to be mainly along the Allegheny Mountains, or near them. E. S. Dingle tells me that he has but one record for coastal or southern South Carolina, April 24, 1929; and Arthur T. Wayne (1910) does not include it in the birds of that State.
According to Dr. Chapman’s (1907) data, nearly a month (25 days, to be exact) elapses between the average dates of arrival at Atlanta, Ga., and arrival at Scotch Lake, New Brunswick. And on the interior route it seems to take just a month for the birds to travel from southern Texas to Aweme, Manitoba.
Nesting: My local experience with the nesting of the chestnutsided warbler dates back to the old “ministerial road” in Rehoboth, Mass., a typical locality in which to find the nests of this warbler. This narrow, neglected, country road skirted the border of the village cemetery, with an open field on the other side, while between the stone wall that bordered the field and the road was a long narrow strip of very small trees and underbrush, mainly hazel bushes. Along the quarter-mile stretch of this road we could always count on finding several pairs of this warbler nesting in the hazel bushes, generally at heights of 2 or 3 feet in the thickets of small bushes; one nest was as low as 14 and one only 18 inches above the ground. We found numerous nests elsewhere along the edges of country roads, in old neglected pastures, in sproutlands, and about the borders of woodlands, where there was suitable shrubbery. Fully 90 percent of the nests were in hazels, but occasional ones were found in huckleberry bushes, blackberry tangles, hardhacks, or small saplings.
Most of the nests are flimsy affairs and loosely built, the walls so thin that daylight shows through them in one or more places; but some are fairly compactly woven. Four nests before me vary considerably in size and construction. The smallest and most compact measures about 214 by 2½ inches in outside diameter, is about 2 inches high externally, and the inner cavity is about 134 wide and 13/4 inches deep. The largest nest measures ~½ by 4 inches in outside diameter, but has about the same height and inside dimensions as the smallest nest and differs from the others in having the whole upper part, or nest proper, made entirely of the finest grasses and extremely fine reddish brown fibers built on a foundation of the usual materials. The other nests are intermediate in size and shape, and are made of both coarse and fine strips of inner bark from cedars or grapevines, weed stems shredded finely, fine grasses, other plant fibers, and some little pieces of plant down; they are lined with very fine grasses, and sometimes also with a little horsehair or cowhair.
I saw two nests’ in the woods near Asquam Lake, N. H., where the black-throated blue warblers were breeding (a location described under that species) ; one of these was built in a mountain laurel bush after the manner of the black-throated blue, and the other was in a crotch in a bunch of maple sprouts in an open clearing. The nests found by Mr. Burleigh (1927a) in northeastern Georgia were all within two feet of the ground, two being in laurels and one in a huckleberry bush.” Some observers have referred to the nests of the chestnut-sided warbler as being firmly, compactly, or strongly built, but my experience usually agrees with that of Mr. Burleigh, who says: “The nests were alike in construction, and distinct enough not to be confused with those of any other species found here, being loosely and somewhat shabbily built.” ‘Nests have been reported by others as located in hazel, huckleberry, raspberry, blackberry, blueberry, barberry, viburnum, spirea, rhododendron, and azalea bushes, and in saplings of oak, maple, birch, beech, and hornbeam. Probably many others might be added to the list.
Mr. Forbush (1929) gives the following account of nest-building, as observed by F. 1-I. Mosher:
The female did all the actual work. She laid straws and plant fibers in a fork of an arrow-wood bush, then went to a tent caterpillar colony and tearing off some of the web bound the forking branches about with it, thus tying them together and forming a deep cup-like framework for the habitation; she also bound the foundation firmly in place with more of the same web, then brought dried grasses or straws and placed them around to form the sides of the nest and bound them to the branches with more caterpillars’ webs. Having finished the sides, she put in a lining of soft grasses, fine rootlets and plant fibers. This nest when completed at the end of five days was much less bulky than the usual nest of the Yellow Warbler, and much firmer, with wails not more than onefourth as thick.
Eggs: Four eggs seem to form t.he usual set for the chestnut-sided warbler, but this sometimes consists of only three, or more rarely five. The eggs are ovate, sometimes tending toward elongate ovate, and they have only a slight lustre. The ground color may be white, creamy white, or very pale greenish white. They are speckled, spotted, and blotched with “auburn,” “bay,” “Brussels brown,” “raw umber,” “chestnut-brown,~~ “cinnamon-brown,” “mummy brown,” or “Mars brown,” with undertones of “dark brownish drab,” “pale brownish drab,” or “light purplish drab.” The color and amount of the markings vary considerably, ranging from eggs that are delicately spotted, or speckled only with drab colors, to those boldly blotched with browns that form a solid ring around the large end, completely covering the undertones. On some the spots are scattered over the entire surface, but generally they are concentrated and tend to form a wreath. A few eggs have the spots confined to a tight, narrow ring, leaving the rest of the surface almost immaculate. The measurements of 50 eggs average 16.7 by 12.4 millimeters; the eggs showing the four extremes measure 18.0 by 12.5,17.3 by 13.2, and 15.2 by 11.7 millimeters (Harris).
Young: The period of incubation for the chestnut-sided warbler seems to be between 12 and 13 days; Frank L. Burns (1915b) says 10 to 11 days, but this seems in error. Only the female incubates. The young remain in the nest 10 to 12 days. Cordelia J. Stanwood MS. says in her notes: “The young come from the eggs blind and limp, covered with short, fine, sparse down and scarcely larger than bumblebees. About the close of the second day, or the beginning of the third day, they commence to open their eyes and the feather spaces begin to show as dark, swollen tracts. Near the end of the sixth day, not far from the beginning of the seventh, the quill stage ends, and the tips of the feathers show beyond the quill casings. By the eighth day the young are pretty well feathered out, and can leave the nest successfully, but, if undisturbed, they usually remain in the nest until the tenth or the eleventh day. While in the nest the young preen, stretch, yawn, beg for food, and utter various calls. Both the parent birds feed the little ones and cleanse the young of parasites and other vermin, although I have noticed in many cases that the female bird generally seems to be the one that burows under the nestlings and cleanses them and the nest lining of annoying pests. * * * All these warblers that I have watched caring for the young in the early stages of nest life begin by feeding the little ones by regurgitation. At the same time an occasional moth or caterpillar that is crushed and mixed with digestive juices is fed directly. At first smaller and softer insects are doled out; later, larger and tougher moths, caterpillars, crane-flies, and the like are fed to them.” Her notes show that the young were fed at frequent intervals, often only one minute apart; sometimes the intervals between feedings were from 5 to 8 minutes, and occasionally as much as 12 minutes.
The parent birds become quite excited when a nest with young is approached, and are sometimes quite bold in their defense of their young; A. D. Du Bois tells me of one that flew at his face, coming within two feet of it as he followed the escaping young; and both parents kept near him, chirping and fluttering.
Plumages: Dr. Dwight (1900) describes the juvenal plumage, in which the sexes are alike, as “above, dark raw umber-brown, obscurely streaked on the back with dull black. Wings and tail dull black, chiefly edged with ashy or plumbeous gray; the secondaries, and tertiaries with olive-yellow, the coverts with buff forming two wing bands yellow-tinged. Below, pale umber-brown, grayer on the throat and sides of head, the abdomen and erissum dull white.”
The first winter plumage, in which the sexes begin to differentiate, is acquired by a partial postnuptial molt, beginning late in June and involving the contour plumage and the wing eoverts, but not the rest of the wings or the tail. Dr. Dwight (1900) describes the young male in this plumage as “above, bright olive-yellow concealing black spots on the back and rump, the upper tail coverts black, tipped with cinereous gray and olive-yellow. The wing coverts black, edged with olive-yellow, two broad wing bands canary-yellow mixed with white. Below, grayish white, pearl-gray on sides of head, throat, breast and flanks, a trace of chestnut striping the flanks terminating in a lemonyellow spot. Conspicuous white orbital ring.” The young female is similar, but the white below is duller, the sides are grayer, and the chestnut stripes are lacking.
The first nuptial plumage is acquired by a partial prenuptial molt in late winter or early spring, that involves most of the contour plumage and the wing coverts, but not the rest of the wings or the tail. Young and old birds are now indistinguishable, except for the browner wings and tail of the young bird. The colors of the female are duller and less intense than those of the male in this and in subsequent plumages.
Subsequent molts consist of a complete postnuptial molt in July and August, and a partial prenuptial molt as in the young bird. Adult females in the fall have some chestnut on the sides, but not so much as the males.
Food: The chestnut-sided warbler is almost wholly insectivorous, though it has been known to eat a few seeds or berries when hardpressed for food. Its foraging range is between the ground and the tops of small trees, or in the lower branches of some of the larger trees; but mainly it gleans through the foliage of shrubbery or low plants, seldom seeking its food on the ground. The insects mentioned under the food of the young are all doubtless eaten regularly by the adults; when securing tent caterpillar webs in nest building, it probably does not object to eating a few of the smaller caterpillars but the large, hairy ones may be refused. Spiders are eaten to some extent. No very comprehensive study of the food seems to have been made, but Forbush (1907) makes this general statement: “The food of the Chestnut-sided Warbler is such that the bird must be exceedingly useful in woodland and shrubbery, and in orchard and shade trees as well, whenever it frequents them. It is probable that at times it destroys considerable numbers of parasitic hymenoptera, as it is rather expert as a flycatcher; but it is very destructive to many injurious beetles and caterpillars, being one of the most active consumers of leaf-eating insects. Small borers or bark beetles, plant bugs and plant lice, leaf hoppers, ants, and aphids are eaten.” Professor Aughey (1878) reports that a stomach examined in Nebraska contained 17 locusts and 21 other insects. F. H. King (1883), reporting for Wisconsin, mentions one eating a small grasshopper and canker worms that were feeding on oaks, hazel, hickory, plum, cherry, apple, pear, and currant. Du Bois tells me of one he watched gleaning its food in an elm tree: “In order to secure insects from the under side of an elm leaf, he hovered like a hummingbird at a flower, and thus picked the food from the leaf while poised in the air.” Forbush (Chapman, 1907) writes:
A Chestnut-sided Warbler was seen to capture and eat, in fourteen minutes, twenty-two gipsy caterpillars, that were positively identified, and other insects that could not be seen plainly were taken during that time. * * A Chestnut-sided Warbler took twenty-eight browutail caterpillars in nbout twelve minutes. When we consider that the short hairs on the posterIor parts of this caterpillar are barbed like the quills of a porcupine and will penetrate the human skin, causing excessive irritatIon and painful eruptions, we may well wonder if the lIttle bird lived to repeat this performance. But many small birds eat these caterpillars at a time when probably the noxious hairs have not fully developed, and others seem to have learned to divest the larger caterpillars of their hairs hy beatiag and shaking their prey and thus loosening the hairs, which are shed as the porcupine sheds its quills. The insect is then eaten with Impunity and even fed to the young birds.
Audubon (1841) tells us that five chestnut-sided warblers, taken during a light fall of snow in May, had eaten nothing but grass seed and spiders.
Behavior: The chestnut-sided warbler is one of the prettiest of the wood warbiers, some regarding it as quite the prettiest. It is certainly one of the most attractive, as it flits about in the roadside shrubbery near us, with its tail elevated, its wings drooping, and its pure white breast swelling as if wit.h pride in its beauty. It is a sprightly, active little bird and far from timid, allowing a near approach as it busily gleans among the foliage or darts out to seize some flying insect. On its nest, which is usually well screened among the leaves, it will sit quietly, confident of its concealing coloration, until we can almost touch it; then su~1denly it is gone, out of sight under the bushes; but it soon appears again, nervously flitting about in the taller bushes or trees to scold at our intrusion.
The following note on the behavior of the parent birds at the nest is contributed by Dr. Alexander F. Skutch: “Following the parents as they carried food, I found a nest of the chestnut-sided warbler situated 3 feet above the ground in the midst of a clump of Cornu8 racemosa on a scrubby hillside near Ithaca, N. Y. It contained two half-grown cowbird nestlings, which squealed a little as I took them in hand, and drove the poor, misguided foster-parents to frenzied efforts to entice me from the nest. The male warbler fluttered from twig to twig in front of me, vibrating his wings and spreading his tail; while his mate descended to the ground beneath the dogwood clump, where she crouched on the dead leaves with vibrating wings and spread tail, moving forward slowly and lamely, after the usual manner of distressed parents. I squatted down in the midst of the bushes the better to see her; and the male, becoming uncommonly bold and loudly chirping his protests, displayed so close before me that every most delicate marking of his plumage was visible: The golden crown, the white sides of the head, the rich chestnut bands along the flanks and sides, and every streak of black and white and gray on the wings and back and tail. I might have reached forward and touched him, had he only remained still. On the following day, the performance was repeated for my benefit.”
Voice: Aretas A. Saunders contributes the following full account of the songs of this warbler: “The chestnut-sided warbler is one that has two different songs, which show seasonal differences, so that they may be referred to as territory and nesting songs. The territory song is the first to be heard, during migration and upon the first arrival on the nesting grounds, while the nesting song is not commonly heard until nesting is established. During the nesting period both songs are to be heard. In common with other species that have two songs, the territory song is fairly definite in form but the nesting song is exceedingly variable. Bot.h have the same quality; t.hey are quite loud, of musical quality, but rather chatterlike and not especially sweet, nor are they so pleasing as those of other musical warblers of this genus’.
“The territory song consists of 4 to 9 notes on a medium pitch, usually rhythmic and of even length, followed by a louder, high-pitched, strongly accented note, and then by a lower terminal note. This is the song commonly translated as very, very, pleased to meetcha. In all but 3 of 30 records of this song the beginning notes are 4, 5, or 6 in number. In 20 records the first notes are single notes, and in the other 10 they are 2-note phrases. This song is always rather short, varying from 12/5 to 14,~ seconds.
“The nesting song is so variable that it is difficult to say .about it much that is definite. Some notes, near the end of the song, are usually high-pitched and strongly accented, but there are numerous exceptions to this. Of 41 records, 19 are composed wholly or mainly of slurred notes, while 21 are single notes or 2-note phrases in a loud, rapid chatter. In the slurred songs the notes are run together. In some records the notes are continuous throughout, without a pause. In the non-slurred songs the notes are distinctly separate. The nesting song is somewhat longer than the territory song, varying from 13/5 to 24,~ seconds.
“The pitch of both songs is about the same, varying from E”‘ to A'”‘, a range of two and a half tones more than an octave but about an octave lower than that of such species as the blackpoll and the Blackburnian. The song is to be heard from the arrival of the bird in migration till the midle of July. The average date of the last song in Allegany State Park, in 14 years of observation, is July 17. The earliest is July 12, 1931, and the latest July 24, 1927.”
Albert B. Brand (1938) gives the approximate mean number of vibrations per second in the song of the chestnut-sided warbler as 5,125, with the highest having 8,775 and the lowest 3,100 vibrations per second. This compares with a mean of 8,900 for the black-poll warbler and 8,000 for the grasshopper sparrow, or an average of 4,000 for passerine songs in general. Francis II. Allen tells me he once found one “with a song consisting of a hurried repetition of a single note as wit-wit: wit-wit-wit-wit-wit-wit. Sometimes this’ was followed by the characteristic warble of the weaker song, and only with this addition was the song recognizable as t.hat of the chestnut-sided warbler. The call note of the species is a thick chip with an L in it.” Miss Stanwood (MS.) writes the song as “wee-wee-‘wee-wee-chi-teewee.”
It seems to me that the rhythm of the ordinary song can be well expressed in human words, or catch phrases; for instance, to Sidney E. Ingraham (1938) it sounded like: “I wish, I wish, I wish to see Miss Beecher! except that we should normally need three or four seconds to say it, whereas Miss Beecher’s lively little friend takes scarcely more than one second. The song is much more like an emphatic sentence made up of words than it is like a phrase of abstract music. The rhythm, of course, is very familiar, actually that of iambic blank verse, rising with force and intention to a climax. Harmonious intervals are lacking, but there are complex inflections ending with the characteristic, explosive little slur up and down.” Other catch phrases seem to call the song to mind quite vividly, are very, very glad to meet you (Iloffmann, 1904), or Ralph B. Simpson’s (Todd, 1940) dis-disdie-dismiss-you, both with a strong accent on the penultimate syllable. This is, of course, the easiest song to recognize, and the only one the amateur is likely to have firmly fixed in his mind.
Field marks: The chestnut-sided warbler is one of the easiest of the family to recognize, as both sexes are much alike, the colors of the female being only a little more restricted and duller. The yellow crown, two yellowish wing bars, chestnut sides, and pure white breast, together with the black and white head pattern, are all conspicuous field marks for the adults. The young bird in fall plumage lacks the bright yellow crown and most of the chestnut sides, the upper parts being bright greenish yellow and the under parts grayish white, but it has the wing-bars and a white eye ring.
Enemies: This warbler is well known to be one of the commonest victims of the cowbird, and Dr. Friedmann (1929) records two cases in which the egg of the imposter had been buried in the bottom of the nest.
Harold S. Peters (1936) mentions one louse and one mite as external parasites on this species.
Winter: The following notes are contributed by Dr. Alexauder F. Skutch: “While the black and white warbler spreads in winter over a vast area and appears to be nowhere really common, the chestnutsided warbler does exactly the reverse, crowds in winter into an area far smaller than its breeding range, and becomes there, during half the year, one of the most abundant of birds. Known in northern Central America only as a rarely recorded bird of passage, this warbler winters in great numbers in Costa Rica and Panami In these countries, it appears to be equally well represented in the lowlands of both the Caribbean and Pacific sides, and continues to be abundant upward to an elevation of about 4,000 feet, above which it rapidly decreases in numbers. There appear to be no definite mid-winter records for altitudes above 5,000 feet, although as a transient it is sometimes found considerably higher.
“In the lofty lowland forests of Costa Rica and Panama the chestnut-sided warbler is, during the period of its sojourn, the one abundant member of the family, whether migratory or resident. It is by no means restricted to the forest but is found wherever trees grow fairly close together, as in coffee plantations with their planted shade trees or along tree-bordered rivers flowing through the cultivated lands. It habitually forages among the crowns of the trees, usually well above the ground. Solitary in disposition, it does not form true flocks; but because of its great abundance several are at times seen in neighboring trees. By early March, the males, which at the time of their arrival are hardly to be distinguished from the females, are clad in their attractive nuptial dress. On April 5, 1937, among the forests of southern Costa Rica, I found a male so attired who repeated over and over a subdued version of his song: an unusual event, for these warbiers seldom sing while in Central America.
“The chestnut-sided warbler has not been known to arrive in Central America before the second half of September, a late date for warbiers. By the beginning of October, it becomes numerous; before the end of April, it has vanished.
“Early dates of fall arrival in Central America are: Guatemala: Chimoxan, September 27 (Griscom). Honduras: Tela, October 1, 1930. Costa Rica: San Jos6, September 25 (Underwood), and September 28 (Cherrie) ; El Hogar, September 27 (Carriker) ; Basin of El General, September 15, 1936, and October 3, 1942.
“Late dates of spring departure from Central America are: Panam~: Barro Colorado Island, Canal Zone, April 6, 1935. Costa Rica: Basin of El General, April 15, 1936, April 21, 1937, April 25, 1939, April 20, 1940, April 12, 1942, and April 17, 1943; San Jos6, April 24 (Cherrie) ; Pejivalle, April 28, 1941. Guatemala: Motagua Valley, near Los Amates, April 24, 1932.”
Range: Eastern North America to Panama.
Breeding range: The chestnut-sided warbler breeds north to central Saskatchewan (Emma Lake and Hudson Bay Junction); southern Manitoba (Duck Mountain, Lake St. Martin, and Hillside Beach); central Ontario (Kenora, Chapleau, and Lake Abitibi); and southern Quebec (Blue Sea Lake, Quebec, and Gasps). East to southeastern Quebec (Gasp~) ; Nova Scotia (Antigonish, Halifax, and Yarmouth); and the coast of New England south to Martha’s Vineyard. South to southern Massachusetts (Martha’s Vineyard) ; southern Connecticut (Saybrook, New Haven, and Bridgeport); northern New Jersey (Elizabeth and Morristown); southeastern Pennsylvania (Berwyn); northern Maryland (Reisterstown); south through the mountains of Virginia, West Virginia, North Carolina, South Carolina (Caesars Head and Highlow Gap); to central northern Georgia (Brasstown Bald [first breeding record for the State, 1925], Mount Oglethorpe, and Burnt Mountain) ; southwestern Kentucky (Log Mountain and Black Mountain); central and northwestern Ohio (Columbus and Toledo); northern Illinois (Chicago and Lacon); and central Iowa, rarely (Coralville, Grinnell, and Des Moines). West to central Iowa (Des Moines) ; central to western Minnesota (Minneapolis, Brainerd, Walker, and White Earth) ; central northern North Dakota (Turtle Mountains); southwestern Manitoba (Carberry); and south-central Saskatchewan (Valeport, Wingard, and Emma Lake).
There is a single record for Alberta of a specimen taken at Red Deer, probably only casual.
Winter range: The winter home of the chestnut-sided warbler is in Central America from southern Nicaragua (Rio Escondido) throughout Costa Rica and western PanamA (Barro Colorado, Canal Zone, and Chitr~).
Migration: L ate dates of spring departure from the winter home are: Panama: Barro Colorado, Canal Zone, April 6. Costa Rica: El General, April. 25. British Honduras: Cayo District, April 27. Tamaulipas: Cafi6n ~Cavelleros, May 16.
Early dates of spring arrival are: Alabama: Anniston, April 16. Georgia: Macon, April 16. South Carolina: Columbia, April 10. North Carolina: Raleigh, April 19. Virginia: Naruna, April 17. West Virginia: Bluefield, April 26. District of Columbia: Washington, April 19. Pennsylvania: Berwyn, April 23. New York: Geneva, April 22. Massachusetts: Taunton, April 25. Vermont: Burlington, May 1. Maine: North Livermore, May 1. Nova Scotia: Halifax, May 4. New Brunswick: Scotch Lake, May 9. Quebee: East Sherbrooke, May 5. Louisiana: New Orleans, March 21. Mississippi: Gulfport, April 14. Arkansas: Delight, April 12. Tennessee: Athens, April 10. Kentucky: Bowling Green, April 26. Indiana: Richmond, April 22. Ohio: Cincinnati, April 25. Michigan: Ann Arbor, April 20. Ontario: Guelph, May 4. Missouri: St. Louis, April 27. Iowa: Iowa City, April 30. Wisconsin: Madison, April 30. Minnesota: Waseca, April 30. Texas: Corpus Christi, March 24. Nebraska: Stapleton, April 25. South Dakota: Lake Poinsett, May 12. North Dakota: Harrisburg, May 15. Manitoba: Margaret, May 14. Saskatchewan: Regina, May 15.
Late dates of the spring departure of transients are: Alabama: Long Island, May 15. Georgia: Atlanta, May 23. South Carolina: Spartanburg, May 18. North Carolina: Greensboro, May 19. Virginia: Charlottesville, May 23. District of Columbia: Washington, June 2. Louisiana: Thibodaux, May 3. Mississippi: Corinth, May 16. Arkansas: Winslow, May 20. Tennessee: Chattanooga, May 20. Kentucky: Lexington, May 15. Iowa: Sioux City, June 4. Texas: Amarillo, May 25. Oklahoma: Kenton, May 21. Kansas: Topeka, May 20. Nebraska: Omaha, May 28. North Dakota: Cando, June 1.
Late dates of fall departure are: Manitoba: Aweme, September 22. North Dakota: Wilton, September 24 (bird banded). South Dakota: Yankton, September 23. Kansas: Osawatomie, October 12. Minnesota: Minneapolis, September 15. Wisconsin: Oshkosh, October 10. Iowa: Davenport, October 2. Ontario: Kingston, September 29. Michigan: Ann Arbor, October 11. Ohio: Oberlin, October 12. Illinois: Lake Forest, October 4. Kentucky: Bowling Green, October 20. Tennessee: Memphis, October 21. Mississippi: Ariel, October 19. Quebec: Quebec, August 28. New Brunswick: Saint John, September 10. Maine: Phillips, September 17. New Hampshire-Hanover, September 19. New York: Rhinebeck, October 8. Pennsylvania: Berwyn, October 15. District of Columbia: Washington, October 14. West Virginia: Bluefield, October 5. North Carolina: Highlands, October 18. South Carolina: Clemson College, October 26. Georgia: Round Oak, October 27. Alabama: Birmingham, October 18.
Banding: Like most warbiers, few of the chestnut-sided have been banded. One return is of some interest. It was banded as an adult at Holderness, N. H., on June 25, 1926, and was retrapped at the same station on July 3, 1927.
Casual records: In 1887 a specimen was collected near Nanortalik, Greenland, four have been taken in western Cuba, in 1940 and 1941, and one was collected at Cheyenne, Wyo., on May 23, 1889. In Colorado a specimen was taken at Barr Lake, May 16, 1933; one was reported near Denver on May 31, 1935; and another at Boulder, April 29, 1942~ In California, one was reported at Sherwood, Mendocino County, September 21, 1908, and another was caught in a banding trap, September 24, 1946, at Manor, Mann County. There is one record for New Providence, Bahamas, without date.
Egg dates: Massachusetts: 86 records, May 22 to July 2; 64 records, May 30 to June 9, indicating the height of the season.
New York: 27 records, May 30 to July 5; 14 records, June 1 to 9.
Pennsylvania: 18 records, May 27 to June 17; 10 records, May 3i to June 7 (Harris).