Tennessee warblers are small, with an average length of only 12 centimeters. In all plumages the upperparts are a vibrant olive green, brightest on the lower back and rump. All Tennessee warblers also have a distinctive black eye-stripe, thin white supercilium, and white and gray auriculars. Juvenile Tennessee warblers are a duller olive color above, and are more yellow below. The forehead, crown and back of the neck of spring adult males is medium gray and contrasts with the olive upperparts. Rare individuals have been known to possess a few rufous crown feathers. The under-parts are dull white, tinged with yellow across the breast and flanks. (Baird, 1967; Curson, 1994; Dunn and Garrett, 1997; Sealy, 1985)
First spring males are very similar to adult spring males except the primaries and rectrices are browner and more worn. Spring adult females are olive-gray on the forehead, crown, and back of the neck, contrasting slightly with the rest of the upperparts. The supercilium, auricular area, throat, breast, flanks and sides are washed with variable shades of yellow. First spring females are not easily distinguishable from spring adult females, except the primaries and rectrices are browner and more worn.
Fall adult males looks like spring adult males except that the gray feathers of the forehead, crown, and hind neck are tipped with olive. Also, the throat and breast are washed with light yellow. The flanks are gray or light olive, and the primaries and rectrices are gray tipped green. In first fall males the upperparts are olive green and brightest on the lower back and rump. The supercilium is yellow, and auriculars are olive-yellow. The chin, breast, sides, flanks, and throat range from lightly to strongly colored with yellow or yellow-olive. First fall males have browner and less green edgings than fall adult males. The findings of the Monomoy Research Station of the Massachusetts Audubon Society conclude that first fall males lack an incubation patch, have a wing length of 62mm, and have bleached primary tips. Fall adult females are not easily distinguishable from fall adult males in the field. First fall females are very similar to first fall males and fall adult females. (Baird, 1967; Curson, 1994; Dunn and Garrett, 1997; Sealy, 1985)
Tennessee warblers have been confused with similar species such as orange-crowned warblers (Vermivora celata), Philadelphia vireos (Vireo philadelphicus), and warbling vireos (Vireo gilvus). However, Tennessee warblers have shorter tails and more pointed wing tips than orange-crowned warblers. Philadelphia and warbling vireos are larger, have hooked bills, and are less energetic. (Baird, 1967; Curson, 1994; Dunn and Garrett, 1997; Sealy, 1985)
Tennessee warblers breed across most of the northern United States including: northern Minnesota, northern Wisconsin, the Upper Peninsula of Michigan, northeastern Maine, the Adirondack Mountains of New York, and locally in northern New Hampshire. Tennessee warblers also breed as far north as southern Yukon, in central British Columbia, and in adjacent areas of southern Alaska. Breeding stretches east to Newfoundland. In late August they migrate from their breeding grounds south across the Gulf coast and arrive on wintering grounds around October. Eastern populations move along the Atlantic coast to Florida, through Central America to Columbia, Venezuela, and Ecuador. The same route is followed in spring. Return migration begins in April with arrival at the breeding grounds by May. (Curson, 1994; Harrison, 1984)
In its breeding range V. peregrina lives in deciduous and coniferous forests, and alder and willow thickets. In all habitats it is linked to shrubs, primarily speckled alder. For instance, in northern Maine it occurs in spruce-fir forests, alder bogs, open white cedar-tamarack-black ash bogs and among coniferous saplings. Migration paths occur through all types of woodlands. For example, along the northern Gulf Coast during spring migration many individuals occupy scrub-shrub, pine forest, and bushes along dunes. Some fall migrants were reported in dry and wet forest, coastal areas, and urban areas. In the winter range Tennessee warblers can be found in open second-growth woodland, wooded shorelines, forest edge, and gallery forests. Tennessee warblers are the most abundant warbler in the coffee plantations of Central America. (Curson, 1994; Rimmer and McFarland, 1998)
Like many wood warblers, Tennessee warblers have a monogamous mating system. Pair formation is initiated after arrival on breeding grounds in the late springtime. There is usually only one brood per season, but if an early nest failure occurs there may be a second brood attempt. Males are very territorial during the breeding season. (Rimmer and McFarland, 1998)
The cup-shaped nest is well concealed in sphagnum moss, or at the bottom of a small tree or shrub. The rim of the nest is flush with ground level. It is made of dead grass, weed stems, and sometimes dried leaves and twigs. The inner lining consists of fine grasses mixed with deer, moose, porcupine, or horse hair. The incubation period is 11 to 12 days, and time to fledging is another 11 to 12 days. The chicks hatch within 24 hours of each other. The eggs are white, speckled or sometimes blotched with chestnut or pale purplish markings. The ovate eggs are smooth to the touch and have an average length of 15.63 mm and width of 12.27mm. The incubation patch is only developed by the female. The earliest date of a fully developed patch is the beginning of June. (Rimmer and McFarland, 1998)
Females spend the majority of their time brooding young. Both males and females feed the young and attend fledglings, but it is unknown if the families stay together beyond breeding. (Rimmer and McFarland, 1998)
There is little data on the annual and lifetime reproductive success, age at first breeding, time between breeding, and life span. Causes of mortality include: parasitism by blood parasites and predators on eggs or nestlings. (Rimmer and McFarland, 1998)
In migration, birds are killed in Florida at smokestacks, buildings, radio and television towers, and ceilometers. (Taylor and Kershner, 1986)
Tennessee warblers are active birds, flitting among foliage and making short flights to reach leaf tips while searching for food. They sometimes hovers while foraging, and descend through vegetation after fallen prey. Tennessee warblers join mixed-species flocks during migration, especially in the fall. Physical interactions such as chasing and fighting occur on wintering grounds where individuals fight for nectar. They are active during the day. (Rimmer and McFarland, 1998)
Territories are established soon after arrival on breeding grounds. They may be located closely together, as evidenced by the proximity of singing males. Males are very territorial during the breeding season, defending their territories by counter singing. In winter grounds, individuals establish territories around nectar sites. (Rimmer and McFarland, 1998)
Only males sing. The calls given during flight are a soft, sharp tsit and a thin see. The song is generally a two- or three-parted song. The components may differ in pitch, time and loudness. The notes are loud, rapid, unmusical and staccato. On average, the song is comprised of seventeen notes. The length of a song ranges from fourteen to thirty-two seconds, and an individual may sing many variations of the song in a short period. Sometimes loudness increases towards the end of the song, and sometimes the opposite is true. Males are persistent singers during the breeding season, repeating songs six to nine times per minute from dawn until midday. There is also a correlation between foraging height and song pitch. Males sing during migration and while foraging in flowering trees on the wintering grounds. The calls vary from loud chips during food defense to soft zeep calls during intra- and interspecific flocking. There are no known nonvocal sounds. (Bent, 1953; Curson, 1994; Rimmer and McFarland, 1998)
Tennessee warblers use their thin bills to glean less active prey from foliage. The bill size is an adaptation used for probing movements and the lack of rictal bristles aids in nectar feeding. During the breeding season they feed on invertebrates such as lepidopteran caterpillars from the outer foliage of trees and shrubs. They rarely hover, foraging on invertebrates mainly using aerial attacks. Tennessee warblers are recorded in large numbers at spruce budworm (Choristoneura) outbreaks. During the migratory season the diet includes: invertebrates, nectar and tropical fruits, including Didymopanax morototoni, Miconia argentea, and Xylopia frutescens. (Rimmer and McFarland, 1998)
Reported predators of Tennessee warbler eggs and nestlings are red squirrels, skunks, weasels, gray jays, martens, and garter snakes. Tennessee warblers are cryptically colored and remain vigilant to protect against predators. (Rimmer and McFarland, 1998)
There is little information on the role V. peregrina plays in the ecosystems they inhabit.
There are no known adverse effects of Vermivora peregrina> on humans.
The noisy, staccato songs of Tennessee warblers mark the beginning of spring songbird migration in North America. These are popular birds among birdwatchers. (Griscom and Sprunt, 1957; Morse, 1989; Rimmer and McFarland, 1998)
Tennessee warblers are protected by the Migratory Bird Treaty Act. There exist other regulations to preserve the health of this species. For instance, due to aerial spraying of chemical insecticides to control spruce budworm outbreaks in North America, thirty-eight percent of sampled Tennessee warblers had serious brain damage leading to higher fatality rates. Now, regulations such as Ultra Ultra Low Volume (UULV) aerial spraying has diminished the impact of pesticides on this species. (Rimmer and McFarland, 1998)
Tanya Dewey (editor), Animal Diversity Web.
Elizabeth Atwood (author), Michigan State University, Pamela Rasmussen (editor, instructor), Michigan State University.
Baird, J. 1967. Arrested molt in Tennessee Warbler. Bird Banding, 38: 236-237.
Bent, A. 1953. Life Histories of North American Wood Warblers. Washington: United States Government Printing Office.
Curson, J. 1994. New World Warblers. Bedford Row, London: Christopher Helm (Publishers) Ltd..
Dunn, J., K. Garrett. 1997. A Field Guide to Warblers of North America. United States of America: Peterson Field Guides and Peterson Field Guide Series.
Griscom, L., A. Sprunt. 1957. The Warblers of America. New York: The Devin-Adair Company.
Harrison, H. 1984. Wood Warblers' World. New York: Simon and Schuster.
Morse, D. 1989. American Warblers. United States of America: Harvard University Press.
Rimmer, C., K. McFarland. 1998. Tennessee warbler (Vermivora peregrina) In The Birds of North America, No. 350. Philadelphia, PA: A. Poole and F. Gill.
Sealy, S. 1985. Analysis of a sample of Tennessee Warblers (Vermivora peregrina) window-killed during spring migration in Manitoba, Canada. Bird Bander, 10: 121-124.
Taylor, W., M. Kershner. 1986. Migrant birds killed at the Vehicle Assembly Building (VAB), John F. Kennedy Space Center. J. Field Ornithol, 57: 142-154.