New World warblers

(Parulidae)

Class Aves

Order Passeriformes

Suborder Passeri (Oscines)

Family Parulidae

Thumbnail description
Small- to medium-sized songbirds with nine primaries (outer flight feathers); very fine, thin bills; and often with colorful plumage

Size
4–7.5 in (10–19 cm)

Number of genera, species
About 28 genera; 126 species

Habitat
Varies among species from heavily wooded deciduous and coniferous forests, marshes, and swamps to semi-open shrubby areas

Conservation status
Critically Endangered: 3 species; Endangered: 5 species; Vulnerable: 6 species; Near Threatened: 7 species

Distribution
North, Central, and South America, and the West Indies

Evolution and systematics

The wood warbler family (Parulidae) was once, and occasionally still is, split into two subfamilies. The "wood warblers proper" (Parulinae) includes about 26 genera and 116 species, and are most numerous in North America. The "bananaquits" (Coerebinae) has one species, which is common in the Caribbean. Many classifications, including the one currently in use by the American Ornithologists' Union (AOU), now place that species in its own family, the Coerebidae. In addition, some classifications also place the nine species of conebills (Conirostrum spp.) in the Parulidae, which would change the family totals to 27 genera and 125 species. Various additional changes have occurred over the years, and several will be addressed below.

As one of the largest bird families, the Parulidae presents a number of challenges to taxonomists, and the most vexing of these center around whether a group of birds warrants the title of species, subspecies, or simple variant. Perhaps the most well-known example involves a group of birds that have fallen under four common names: the blue-winged, golden-winged, Brewster's, and Lawrence's warblers. The two prominent groups—the blue- and golden-wings—look quite different. A blue-wing (Vermivora pinus) has a golden head and underside, with a darker back, a black eye stripe, and a blue-gray tail and wings, which feature two conspicuous white wing bars. A golden-wing (Vermivora chrysoptera) has a yellow crown and two yellow wing bars, and the rest of the bird resembles the white, black, and gray pattern of a chickadee, with a gray back and wings, white underside, and black eye mask and throat. Historically, the two birds were separated geographically, with the blue-wings tending toward the central United States and the golden-wings remaining in the East. Both preferred the low bushes of semi-open, shrubby woodlands often at the edges of forests, and remained fairly well separated as long as large expanses of open field existed between them. The open fields persisted into the early and mid-1800s, but woodlands slowly began to take over the fields, and the blue-wings expanded their range to overlap that of the golden-wings. Although the two looked dissimilar and had distinct songs, they interbred and produced fertile offspring. The confusion escalated when birders identified the offspring as two additional species, the Brewster's and Lawrence's warblers. A Brewster's looks like a blue-wing, except that its wing bars are yellow instead of white, and it has a whitish instead of yellow underside. The

Lawrence's, on the other hand, resembles the golden-wing, but with a yellow rather than white underside.

For years, taxonomists were left scratching their heads. The first to consider the possibility that blue- and golden-wings were the same species, and were producing hybrid offspring, was probably John James Audubon, who apparently examined one of the earliest collected specimens of a Brewster's warbler. Through his astute observational skills, he noted the similarities to the blue-winged and golden-winged warblers, and asserted in a letter dated 1835 that the three were likely the same species. His later writings made no reference to this contention, however, and the puzzle continued for several decades until the early 1900s when birder Walter Faxon found a mating pair made up of a female blue-winged and male golden-winged, and discovered the progeny all to be Brewster's warblers. Lawrence's warblers were later similarly discovered to be hybrids. Although the findings settled the classification of Lawrence's and Brewster's, the status of the blue-winged and golden-winged warblers was much less certain. Currently, taxonomists regard them as two separate species, as they do with some other occasional interbreeders, like the hermit (Dendroica occidentalis) and Townsend's warblers (D. townsendi). On the other hand, taxonomists have determined that two formerly separate species, known as the myrtle and Audubon's warblers, are actually one species with two plumage patterns. The birds, which still retain their common names (Audubon's warbler in western North America and myrtle warbler in the East), are now both listed as the yellow-rumped warbler (D. coronata).

The phylogenetic relationship of Parulidae to other bird families is also less than clear-cut. Some taxonomists have placed them closest to the tanager family, Thraupidae (sometimes treated as a subfamily, Thraupinae, of Emberizidae), while others feel they are nearest to the New World finches family, Emberizidae. In some classifications, the wood warblers are actually listed as a subfamily, Parulinae, within Emberizidae.

Without a substantial fossil trail to follow, taxonomists in the past relied mainly on anatomical, morphological, and behavioral characteristics to deduce the family's evolutionary history. DNA-comparison technology, however, has now allowed scientists to obtain a different view of phylogenies. One group compared the genetic code of different birds, and determined that the wood warblers are genetically so similar to other groups of birds, including the blackbirds, buntings, cardinals, and tangers that they together should make up just one of three subfamilies within the family Fringillidae. While the work is intriguing, most birders, including the AOU, still use the more traditional arrangement with the wood warblers in their own family, the Parulidae. The AOU has, however, determined that one of the warblers is different enough from the other wood warblers to justify its own family. That bird is the olive warbler (Peucedramus taeniatus), which may reside alone in the Peucedramidae family.

Other taxonomists have used DNA to determine how long ago the wood warblers split from their ancestral rootstock into the many species that occur today. For example, one group compared the timing of the speciation of New World wood warblers vs. Old World warblers (Sylviidae) by studying differences in one specific gene, the mitochondrial cytochrome b gene. From the 13 wood warblers and 8 Old World warblers they studied, they determined that the wood warblers experienced an explosive radiation in the late Pliocene or early

Pleistocene, much later than the other families within the Passeriformes order, including the Old World warblers. The research team suggested that changing environmental conditions in the late Pliocene opened new habitats to the ancestral wood warblers, and speciation followed. Another study conducted by a separate research group also used analyses of mitochondrial DNA to take a closer look at wood warbler phylogeny. In this study, the scientists investigated the Dendroica genus, which includes more than two dozen wood warbler species, and concluded that the Dendroica speciation dated back as far as the late Miocene or early Pliocene, making the extant species the current end-points of ancient lineages.

Although DNA studies may ultimately produce a definitive phylogeny for the wood warblers, much work remains as scientists examine additional species, struggle to sift through the mounting, and sometimes conflicting, genetic data, and determine how to apply the new knowledge appropriately.

Physical characteristics

The Parulidae is a vast group, yet the wood warblers share a number of traits. Most have slender or flat beaks that are pointy, but short. Some wood warblers, like the yellow-breasted chat (Icteria virens) and yellow-rumped warbler, have

more robust bills, while the American redstart (Setophaga ruticilla) sports distinctive rictal bristles, which are stiff, modified feathers at the base of its flat bill. Most wood warblers are small birds, tending toward the smaller side of the family's 4–7.5 in (10.2–19.1 cm) range. They are characterized by legs that look no more sturdy than a toothpick, and have the typical three-toes-forward foot structure of other birds in the Passeriformes order.

Wood warbler plumage ranges widely in color. These "jewels of the forest" generally have yellow, red, black, gray, or green areas of plumage, with yellow and olive the predominant colors within the family. Males of the temperate species are usually much brighter in color and have sharper patterns than do the females, but males of some species become duller and resemble the females in fall and winter. Juvenal plumage is frequently similar to the female's, but duller still. Among the more tropical species, the males and females generally look alike. In some species of wood warbler, like the yellow warbler (Dendroica petechia), the male is slightly larger than the female. A unifying trait among all wood warblers is the presence of nine functional primary feathers. Other song-birds typically have 10.

Another identifying feature of many wood warblers is their seemingly constant movement. They flit from branch to branch, usually giving observers only a quick glimpse of color before they fly off to another spot. A birder can spend hours in the field listening to a common yellowthroat (Geothlypis trichas) or yellow warbler singing nearby, but may be unable to focus the binoculars on anything more than a branch left swaying by the bird that just left.

Finally, one of the most distinguishing characteristics of the wood warblers is their songs, which add greatly to nature's symphony. Prime examples include the Louisiana waterthrush (Seiurus motacilla), an insignificant-looking ground dweller that often utters its loud, pleasant tune to a background of rushing water; and the yellow-breasted chat, which has a loud, flutelike and gurgling song. The ovenbird (Seiurus aurocapillus) is much less melodious, with a blunt cry that sounds like "teacher, teacher." In contrast, the feeble "heeebsss" song of the blue-winged warbler sounds like an insect and is often identified as such by inexperienced human observers.

Distribution

The wood warblers are distributed over almost all of the New World from Alaska and northern Canada to northern Chile and Argentina. More than 50 species breed within the central and eastern portions of North America from about the middle half of the United States to the southern half of Canada.

Many wood warblers are wide-ranging. The yellow warbler and common yellowthroat, for example, breed from coast to coast in North America, throughout the United States and well into Canada and Mexico. On the opposite end of the spectrum, the Kirtland's warbler (Dendroica kirtlandii) occupies a tiny breeding range in north-central Michigan.

Habitat

These songbirds occupy a great number of habitats from thick to semi-open woodlands, to marshes and swamps, to forest edges. They generally prefer areas that have dense shrubs or thickets, where they often spend much of their time. While most favor woodlands or woodland edges, others tend toward more exotic habitats. The hermit warbler (Dendroica occidentalis), for instance, lives in the fairly open coniferous forests along the west coast of the United States, whereas the cerulean warbler (Dendroica cerulea) inhabits the dense deciduous forests in the eastern half of the United States, and the Kirtland's warbler breeds in stands of young jack pines in Michigan. The northern waterthrush (Seiurus noveboracensis) lives in the swamps of Canada, Alaska, and the northernmost United States, while the worm-eating warbler (Helmitheros vermivorus) exists in dry woodlots in the central-eastern United States, and Lucy's warbler (Vermivora luciae) makes a living in the mesquite deserts of the southwestern United States and Mexico.

This family has infiltrated many niches, much as the Old World warblers have done in the Eastern Hemisphere. While individual species of wood warblers are not gregarious during the breeding season, several different species frequently coexist. From a good vantage point along the edge of a forest in the northeastern United States, a birder can expect to hear upwards of eight to 10 different species of wood warblers singing in early summer.

It is important to point out that most of what is known of the wood warblers is based on information collected during the North American species' breeding seasons. Although the species spend about eight months on average in their winter homes and only four in their breeding areas, North America has many more birders, as well as organized research projects, in place to study them.

Behavior

Most North American wood warblers are long-distance migrants. Their regular passage is one of the most striking features of North American bird life. During the height of the spring migration in May, it is possible to see up to 30 species in a day in eastern North America. The North American species winter mainly in Central America and northern South America, but a few resistant species winter in the United States, while others move as far south as Argentina.

Although the birds are fairly small, they travel very long distances between their summer breeding grounds and winter homes, with some species traveling 3,000 mi (4,800 km) and more each way—quite a feat for such a small bird. The birds use almost their entire fat stores during the flight. An American redstart with summer territory in New Hampshire, for example, loses about 50% of its premigration weight during its 1,800 mi (2,900 km) autumn flight to its wintering site in Jamaica. Yellow warblers travel even farther. With residences in Central and South America, but summer breeding grounds reaching into northern Canada and Alaska, the birds can face treks upwards of 3,000 mi (4,800 km).

The birds generally migrate from dusk to dawn during their spring and fall migrations. With top speeds of 30 mph (48 kph), the birds can cover considerable ground—often more than 100 mi (160 km) a night—when wind and weather conditions are right. Upon landing, these energy-starved birds spend little time resting, instead filling the day by filling their stomachs. During these flights, different species will often flock together, presenting a spectacular viewing opportunity for human observers. At night, the warblers are visible as they fly in front of a bright moon. During the day, the multispecies flocks land en masse, making quite a racket while searching for insects. Males and females will chip and chirp in flight and on their feeding forays, and males add to the daytime chatter in the spring by performing a few prebreeding songs.

Once the birds reach the breeding grounds, most wood warblers become territorial toward other birds of the same species. While a 20-acre (8-hectare) New England forest may contain 10 or more different warbler species, males of the same species separate themselves from one another. Territory sizes depend on the availability of food and nesting sites, but usually range from about a third of an acre (0.13 ha) to five acres (2 ha) or more. Males typically rely on their songs and visual displays to ward off intruding males. American redstarts have a particularly elaborate display, involving a succession of circling movements that serve to confirm their territorial boundaries.

In addition to visual cues, wood warblers communicate through their songs, which are used only by the males in all but a few species, and through their calls. Bird calls are the nonmelodic "chips" that both males and females utter year-round. Wood warblers, like all other songbirds in the Oscines

suborder of the Passeriformes, learn their songs. The learning begins within the first week after hatching, with the males learning to sing songs, and the females learning to recognize them. An exception to the rule is the female painted redstart (Myioborus pictus), whose song rivals that of the males of the species.

Feeding ecology and diet

Wood warblers feed mainly on insects, which they seek busily everywhere, much like the Old World leaf warblers. While searching for food, they move on the ground amid grass, on bushes, or in the foliage—in some cases also on tree bark. Several species are able to live and feed together in over-lapping habitats because of the availability of their primary food source, as well as the slightly different feeding habits many exhibit.

Although small arthropods are the main food of wood warblers, some species occasionally take berries, seeds, or even the juice inside fruits. Regardless of their fare, wood warblers have bills suited to the job at hand. Their typically thin and pointy bills allow them to extricate insects and spiders from tiny splits in bark or spaces between grass blades. The sharper bill of many other warblers expands their feeding range into seeds and berries. Species like the myrtle warbler/yellowrumped warbler can only survive the winter in eastern North America by feeding on berries and sometimes seeds. Others, like the blue-winged warbler, have longer bills that provide access to insects buried within flowers. The American redstart is unusual in its bill structure and its feeding habits. Its relatively short and broad bill combine with its quick reflexes and excellent flying ability to give it the tools required for in-flight insect capture, much like the flycatchers (family Tyrannidae).

While wood warblers retain their general feeding habits all year, they typically are territorial among their own species only when they are on summer breeding grounds. During the migratory flights and at their winter residences, most warblers are communal, if not necessarily gregarious. In some species, the males and females separate and tend toward different habitats in the winter, so an observer might spot a group of males in the woods and a small flock of females in a field.

Reproductive biology

The reproductive biology of wood warblers, like most other birds, is highly cyclical. In general, wood warblers follow this annual pattern: following a spring migration, males arrive in their breeding grounds and use their voice and visual displays to set up territories and attract mates. Males and females form pairs that are monogamous at least for the season. Although yearlings engage in the mating activities, they are typically less successful than older birds.

Of all of the warblers' activities, their songs draw the most attention. According to several studies, warblers appear to use one variation of their song to establish and defend territory boundaries, and a second variation to attract females. Several studies have investigated the importance of this song in the female's choice of a mate, as well as the long-term effects of such sexual selection. One study has suggested that a superior singing voice in a male songbird is related to the level of development of specific learning areas in the brain, and that development hinges on how well the male overcame nutritional stresses as a hatchling and young fledgling when those learning areas were forming. The birds that fared best, the author argues, have the most well-developed learning areas with which to build singing and perhaps other skills. By selecting the best singers, then, the females are actually choosing the highest-quality mates.

After a pair forms, the majority of the 53 North American wood warblers remain monogamous for the breeding season, while Central and South American pairs may persist for longer periods. Among some species, females may pair socially with one male, but mate with another. As a result some males help rear hatchlings that are not their own. Among yellow warblers, one of the most common of the North American warblers, females that engage in this so-called "extra-pair mating" most frequently do so with males that are large in size and have extra brown streaking on their yellow breasts, thus perpetuating these male traits through sexual selection.

Nesting is species-specific in wood warblers, and experienced ornithologists can often identify the species just by looking at its nest. Wood warbler nests are frequently cupshaped, and may be on the ground, among grass, in bushes, or on trees, often more than 50 ft (15 m) high. They are usually firm, densely woven structures, generally with an inner lining layer of rootlets or moss. Nonetheless, nests among species in this family exhibit considerable variation. The prothonotary warbler (Protonotaria citrea) makes its nest in tree cavities, while the Louisiana waterthrush prefers a hole dug into a stream bank. Grace's warbler (Dendroica graciae) builds its small cup high on pine branches, but the ovenbird makes a roof of leaves to hide its ground-level nest.

The clutch size varies a great deal within the family, but four eggs per nest is typical of North American warblers and three is common among the tropical genera. Food supply often regulates clutch size, with sparse years producing fewer eggs per pair. The eggs are usually white with pale reddish brown or black markings, sometimes arranged as in a wreath. If the birds breed early enough, they sometimes have time to lay another clutch if the first fails. Through the incubation period, the female stays with the eggs, and the male brings her food. Eggs, on average, hatch in 12 days, at which time both the female and male take on feeding duty. The young fledge in about 10 days, and although they have already reached 90% of their adult weight, they lack adequate flight muscles or coordination. The parents continue feeding them for several more weeks, with the male generally responsible for half the fledglings and the female accountable for the other half. After that, the young birds are on their own.

Conservation status

In the wood warbler family, the IUCN lists seven as Near Threatened, seven as Vulnerable (including one conebill), five as Endangered, and three as Critically Endangered species. Of the Critically Endangered, two are feared to already be Extinct. They are the Semper's warbler (Leucopeza semperi) of the mountains of St. Lucia in the West Indies, and Bachman's warbler (Vermivora bachmanii), a once abundant North American breeding bird that wintered in West Indies' forests. As might be expected, the remaining at-risk species are typified by small ranges, where even small habitat destruction can be disastrous. Of the at-risk species, many breed in North America, including one Near Threatened, five Vulnerable, three Endangered, and two Critically Endangered species.

Vulnerable species include: Pirre warbler (Basileuterus ignotus), elfin-wood warbler (Dendroica angelae), Kirtland's warbler, pink-headed warbler (Ergaticus versicolor), Altamira yellowthroat (Geothlypis flavovelata), white-winged (ground) warbler (Xenoligea montana), and Tamarugo conebill (Conirostrum tamarugense). The Endangered species include: gray-headed warbler (Basileuterus griseiceps), whistling warbler (Catharopeza bishopi), golden-cheeked warbler (Dendroica chrysoparia), black-polled yellowthroat (Geothlypis speciosa), and Paria redstart (Myioborus pariae), which also goes by the common names of Paria whitestart and yellow-faced redstart. Besides the Semper's and Bachman's warblers, Belding's yellowthroat (Geothlypis beldingi) is Critically Endangered and faces extinction from the handful of small sites it occupies in the Baja California peninsula of Mexico.

In addition to the at-risk species, scientists are also concerned about other songbirds, even those with more vast ranges. In the 1970s and 1980s, birders began to notice and report precipitous declines in populations of many common wood warblers, such as the cerulean warbler and the Kentucky warbler (Oporornis formosus), both of which breed in the central and eastern United States. The reports prompted research, which has since found the major culprit to be habitat destruction in the wintering grounds combined with habitat fragmentation in the breeding grounds. Many North American wood warblers share wintering grounds in Costa Rica, Guatemala, and other Neotropical and tropical countries that have undergone extensive deforestation, so scientists have taken a particularly close look at the relationship between habitat loss and songbird declines. A study of American redstarts, a black-and-orange bird that breeds in a swath across North America from western Canada south and east to the Atlantic coast of Canada and the United States, showed that the birds' success in the breeding season relied on the quantity and quality of their wintering habitat in Jamaica. With less habitat to go around, some redstarts wintered in lush, rich forests, while others were relegated to dry scrublands. Those in the rich forests found more food, faced less overall stress, and were in prime condition to leave on their spring migrations up to four weeks earlier than the less fortunate birds eking out a living in the scrublands. The earlier arrival in North America of the healthier warblers meant less competition for choice nesting sites and mates.

Other research has placed the blame for songbird declines on changes in breeding habitat, particularly fragmentation that involves breaking up large expanses of open land, usually with developments. The fragmentation of habitat has obvious impacts on species that require large territories, but the primary detriment to songbirds is that fragmentation paves the way for the many predatory animals that thrive along habitat edges. One particularly devastating animal is the brown-headed cowbird (Molothrus ater), a brood parasite that lays its eggs in the nests of other birds, including warblers. The cowbird hatchlings are much larger and can outcompete with their nest mates for food from the warbler parents, which typically

feed whichever hatchling makes its mouth most available. The cowbird hatchlings become stronger and bigger, and those young warblers that avoid being crushed or simply pushed out of the nest by the cowbird hatchlings usually starve to death. Besides cowbirds, egg-eating raccoons and opossums also flourish in edge areas, and can devastate the warblers that nest on the ground.

Many efforts are now under way to combat warbler declines, and several have been quite successful. The Kirtland's warbler is one example. Due to habitat restoration efforts, populations have risen in recent years, and the bird has been upgraded from its 1994 ranking as Endangered to a 1996 placement at Vulnerable, where it has remained.

Significance to humans

Too tiny to be much of a source of food or feathers, warblers still play an important role in human existence. Perhaps their greatest significance lies in their aesthetic beauty. Nothing lifts the spirit quite like a common yellowthroat alighting just for a moment on a sun-streaked branch, or the bright, tinkling song of a yellow warbler on a warm, late spring morning in the northern woods. These birds fill the skies during migration, breaking the spell of winter in the north, or dance back home to Central and South America in autumn. No other group of animals could take the place of these bundles of energy in inviting people to come outside and revel in nature's splendor.

Species accounts

List of Species

Yellow-breasted chat

Icteria virens

subfamily

Parulinae

taxonomy

Icteria virens Linnaeus, 1758, South Carolina.

other common names

French: Ictérie à poitrine jaune; German: Gelbbrust-Waldsänger; Spanish: Reinita Grande.

physical characteristics

With a length of up to 7.5 in (19 cm), it is the largest wood warbler. Upperparts are olive, throat and breast are bright yellow, and the rest of the underside is white. Face is blackish with a white eye stripe and eye circle, and it sports a plump, conical bill unlike the typical warbler bill of the family. The female and male are similar in appearance.

distribution

Breeds from east to west in the United States, north into southern Canada and south into Mexico. Winters from Mexico south to Panama.

habitat

Prefers to be near water, spending most of its time hidden among tangles and thickets.

behavior

Unlike other warblers that flit among branches, the yellow-breasted chat takes more of a bull-in-a-china-shop approach—

flopping, falling, and tail-swooning through the thickets. Its songs, some of which it performs at night, combine a few melodious bursts interspersed with gobbles, caws, and other less delicate sounds. It also has been described as a ventriloquist in that it can throw its voice and fool even experienced birders.

feeding ecology and diet

Mainly insects, but also eats berries.

reproductive biology

Cup-like nests rest in the tangles and brambles, and typically hold up to six brown-and-purple-speckled eggs. More than one pair may share a nesting site.

conservation status

Not threatened. Widespread and fairly common.

significance to humans

Song and behavior provide enjoyment for birders.

Golden-winged warbler

Vermivora chrysoptera

subfamily

Parulinae

taxonomy

Vermivora chrysoptera Linnaeus, 1766, Pennsylvania.

other common names

French: Paruline à ailes dorées; German: Goldflügel-Waldsänger; Spanish: Reinita Gusanera.

physical characteristics

4.5–5 in (11.4–12.7 cm). The very thin-billed golden-winged warbler has a yellow crown, and two yellow wing bars. The remaining plumage has a white, black, and gray pattern reminiscent of a chickadee, with a gray back and wings, white underside, and black eye mask and throat. The female is similar, but duller, with more olive coloration than gray and black.

distribution

Breed in northern United States, winter in Central America.

habitat

Forest edges and swamps.

behavior

Has a buzzing song. Often seen hanging upside-down on branches, much as chickadees do.

feeding ecology and diet

Mainly insects.

reproductive biology

Breeds in low bushes, building cup-shaped nests on or close to the ground. Average clutch is five to seven speckled eggs that hatch in less than two weeks. Sometimes occurs side by side with blue-winged warblers, and the two produce viable hybrid offspring, known by the common names of Brewster's and Lawrence's warblers.

conservation status

Not threatened, but appears to be on the decline where its habitat overlaps with that of blue-winged warblers.

significance to humans

None known.

Blue-winged warbler

Vermivora pinus

subfamily

Parulinae

taxonomy

Vermivora pinus Linnaeus, 1766, Pennsylvania.

other common names

English: Blue-winged yellow warbler; French: Paruline à ailes bleues; German: Blauflügel-Waldsänger; Spanish: Reinita Aliazul.

physical characteristics

4.5–5 in (11.4–12.7 cm). Golden head with a black eye stripe, golden underside, darker back, blue-gray tail and wings, and two white wing bars. Males and females have similar appearance.

distribution

Breeds in northern United States, winters from Mexico to Panama in Central America.

habitat

Forest edges and swamps.

behavior

Moves rather deliberately through trees, sometimes hanging upside-down from branches. Often pauses for lengths of time on favorite perches.

feeding ecology and diet

Mainly insects.

reproductive biology

Breeds in low bushes, building cup-shaped nests on or close to the ground. Average clutch is four to seven finely speckled eggs that hatch in less than two weeks. Sometimes occurs side by side with golden-winged warblers, and the two produce viable hybrid offspring, known by the common names of Brewster's and Lawrence's warblers.

conservation status

Not threatened. Appears to be replacing golden-winged warblers in areas where they overlap.

significance to humans

None known.

Prothonotary warbler

Protonotaria citrea

subfamily

Parulinae

taxonomy

Protonotaria citrea Boddaert, 1783, Louisiana.

other common names

French: Paruline protonotaire; German: Orangefleck-Waldsänger; Spanish: Reinita Cabecidorada.

physical characteristics

5–5.5 in (12.7—14 cm). Long, thin bill, bright golden yellow and gray plumage, and a fairly short tail. Its name comes from

a resemblance of its plumage to the garb of court clerks, known as prothonotaries. The female is similar but less brightly colored.

distribution

Breed from Florida west to Texas and north to Minnesota, southern Ontario and Pennsylvania. Winters in pristine rain-forest habitats from southern Mexico to Venezuela.

habitat

Wooded swamps.

behavior

Song is a repeated series of "tweets." Often seen poking into the saturated logs of the swamps, where it resides.

feeding ecology and diet

Mainly insects.

reproductive biology

Unusual for warblers, it builds its mainly moss nests in tree holes such as old woodpecker holes, or in nest boxes. Average clutch size is three to eight, with speckled light pink eggs that hatch in about two weeks.

conservation status

Not threatened.

significance to humans

None known.

Black-and-white warbler

Mniotilta varia

subfamily

Parulinae

taxonomy

Mniotilta varia Linnaeus, 1766, Hispaniola.

other common names

English: Black-and-white nuthatch; French: Paruline noir et blanc; German: Kletterwaldsänger; Spanish: Reinita Trepadora.

physical characteristics

4.5–5.5 in (11.4–14 cm). The only bird in its genus, it is an abundantly striped black-and-white bird. Males have a black bib; females do not. The rear toe and claw are unusually long, and ideal for its creeper-like habits.

distribution

Breeds from the southern and central United States and far north into western Canada. Winters from the far southern Gulf states to the northern reaches of South America.

habitat

Coniferous or deciduous forests, particularly common in more northern areas.

behavior

It has a soft, often-repeated "wee-ee" song. It pecks its food out of clefts in the bark of trees, which it searches carefully, usually by working over one tree trunk after another from near the ground by creeping upwards, much as nuthatches (Sitta spp.) do.

feeding ecology and diet

Mainly arthropods.

reproductive biology

It is one of the earliest wood warblers to return to North America in the spring. It builds its nest of strips of bark, moss, grass, and other materials, behind a piece of bark on the lower part of a tree trunk or more frequently on the ground beneath a tree where it covers it partly with leaves. Produces four to five speckled eggs, which hatch in a week and a half.

conservation status

Not threatened. Widespread and common in northern North America.

significance to humans

None known.

Yellow warbler

Dendroica petechia

subfamily

Parulinae

taxonomy

Dendroica petechia Linnaeus, 1766, Barbados. More than six subspecies.

other common names

English: Summer yellow bird, wild canary; French: Paruline jaune; German: Goldwaldsänger; Spanish: Reinita Amarilla.

physical characteristics

4.5–5.5 in (11.4–14 cm). Primarily bright yellow bird with olive hint on upperparts. Breast of male is streaked with rusty color, female has no or only light streaking. Two yellow wing bars are present on its yellow-and-olive-colored wings.

distribution

Breeds in most of North America from Alaska and far northern Canada south to northwest Mexico. Winters from Mexico to Peru.

habitat

Often seen in gardens, its wild habitat includes woods and brushy areas near water.

behavior

Songs are bright and repeated during the breeding season and beyond, often beginning before sunrise. The songs draw the

attention of birders, but the birds seldom sit still long enough for a thorough viewing.

feeding ecology and diet

Mainly arthropods.

reproductive biology

Begin mating shortly after arriving on the breeding grounds in early spring. Occasionally females will socially pair with one male, but mate with another. Eggs can be sired by either male. Nests are typically constructed of grass and plant materials in the crook of a branch about 6–8 ft (1.8–2.4 m) above the ground in small trees or shrubs. Eggs number four or five, often have a grayish or greenish white hue, and hatch in about a week and a half.

conservation status

Not threatened. Their numbers, however, have been affected by cowbird brood parasitism. Yellow warblers often readily rear cowbird young, but occasionally will reject the parasitized brood altogether and built a new nest, often on top of the old one.

significance to humans

None known.

Ovenbird

Seiurus aurocapillus

subfamily

Parulinae

taxonomy

Seiurus aurocapillus Linnaeus, 1766, at sea off Haiti. Two sub-species.

other common names

English: Teacherbird; French: Paruline couronnée; German: Pieperwaldsänger; Spanish: Reinita Hornera.

physical characteristics

5.5–6.5 in (14–16.5 cm). Brownish upperparts, two black stripes on crown of head with a rusty orange patch between. White throat with brown stripes. Underparts are white with mottled-brown breast, somewhat similar in appearance to a wood thrush.

distribution

Breeds in the northern half of the United States from the eastern coast through the Midwest and into Montana, and well into Canada from the Atlantic Ocean to Alberta.

habitat

Mixed and deciduous woods lacking dense bushy undergrowth.

behavior

Instead of flitting from tree to tree in characteristic warbler fashion, it runs about the fallen leaves and tosses them aside in its search for hidden arthropods. It responds to the presence of an intruder, particularly when the latter is near the nest, by flying up, uttering "tick" calls or even by erecting the orange-colored feathers of its crown patch. It also sometimes mimics an injured bird to draw away the intruder. Its song is one of the best-known North American bird songs, and consists of a sequence of "teach-er, teach-er teach-er," which gets progressively louder. The popular name "teacherbird" derives from

the song, which is delivered from the ground or from low to fairly high-placed branches.

feeding ecology and diet

Mainly arthropods, earthworms, and snails.

reproductive biology

Courtship involves in-flight singing, posturing, and pursuit by the males. The ovenbird makes its nests on the ground, using grass and stems topped with leaves for the roof, and grass and hair for the interior lining. The nest resembles a Dutch oven, and is responsible for the bird's common name. Typically lay three to six speckled eggs, which hatch about two weeks later.

conservation status

Not threatened. Their nests, however, are becoming more vulnerable to predators that prefer fragmented habitat, which is becoming more plentiful in their breeding grounds.

significance to humans

Particularly valued for their songs—they are seldom seen but frequently heard.

Hooded warbler

Wilsonia citrina

subfamily

Parulinae

taxonomy

Wilsonia citrina Boddaert, 1783, Louisiana.

other common names

French: Paruline à capuchon; German: Kapuzenwaldsänger; Spanish: Reinita Encapuchada.

physical characteristics

5–6 in (12.7–15.3 cm). Dark olive above, yellow below, and a yellow face. Conspicuous bristles at the angles of its fairly wide bill. Male also has a black cowl that extends from his throat to the top of his head.

distribution

Breeds in the eastern half of the United States from the Gulf states north to central Iowa, Ohio, and parts of New York. Winters in Central America.

habitat

Undergrowth of mature deciduous woods.

behavior

Like a flycatcher, the male often catches flying arthropods on the wing. The females, however, generally forage on foliage and branches nearer ground level. The male's loud ringing song, "wee te wee tee o," proclaims its presence in thickets, often near water. Unlike most other warblers, the sexes frequently segregate in the wintering grounds.

feeding ecology and diet

Mainly arthropods.

reproductive biology

It builds its nest among bushes and climbers. The nest itself is firmly built of leaves and grasses and lined with rootlets or fine grass. The female lays three or four speckled eggs, similar to those of many other wood warblers. The young hatch a little more than a week later. This species typically produces two broods a year.

conservation status

Not threatened.

significance to humans

None known.

Kirtland's warbler

Dendroica kirtlandii

subfamily

Parulinae

taxonomy

Dendroica kirtlandii Baird, 1852, Ohio.

other common names

French: Paruline de Kirtland; German: Michiganwaldsänger; Spanish: Reinita Kirtland.

physical characteristics

A dark gray and yellow bird that reaches 6 in (15.3) in length. The body is essentially split by color, with gray above and yellow below. The underparts are mostly yellow with a bit of gray streaking along the sides. Males are more brightly colored than the females and sport a dark mask, which the females lack.

distribution

Breeds in numbers only in central Michigan. Winters primarily in the Bahamas.

habitat

Jack pine stands, preferring those with younger trees.

behavior

Frequently spotted among jack pine trees, searching for insects and pecking at sap, which they also consume. The males have a distinctive, loud, and somewhat low-pitched song.

feeding ecology and diet

Mainly insects, but also some plant materials and berries.

reproductive biology

Breeding begins shortly after the birds' arrival in the spring. They build their cup-shaped nests of grass and other plant materials,

and conceal them on the ground beneath the branches of young jack pines. Clutch size is generally four or five speckled eggs that are either white or tinged with pink. Hatching occurs about two weeks later.

conservation status

The IUCN Red List for 2000 lists the birds as Vulnerable, an improvement from their 1990 and 1994 rankings of Endangered. The upgraded status results, at least in part, from efforts to improve their habitat. These efforts have included periodic burns of jack pine stands to trigger the stubborn cones to open, release their seeds, and start new growth. Despite the increase in breeding pairs, the species' range is still small enough to warrant the Vulnerable status. It is also one of the birds that has fallen victim to the cowbird's brood parasitism.

significance to humans

They have become the source of some economic benefit in Michigan, as the birds attract visitors, who wish to catch a glimpse of this "poster child" of United States at-risk species.

Cerulean warbler

Dendroica cerulea

subfamily

Parulinae

taxonomy

Dendroica cerulea Wilson, 1810, Hispaniola.

other common names

French: Paruline d'azur; German: Pappelwaldsänger; Spanish: Reinita Cerúlea.

physical characteristics

A blue, black, and white bird that reaches 4–5 in (10.2–12.7 cm) long. Its upperparts are blue to blue-gray with a few black

streaks, and the underparts are mostly white. The wings feature two white bars. The female looks similar, but substitutes a soft olive for the blue plumage, and lacks the black neck ring the males have.

distribution

Breeds mostly in the eastern half of the United States, north into the southernmost points in Ontario, south to North Carolina, and southwest to Louisiana. Winters primarily in rain-forests of northern South America.

habitat

Deciduous forests, particularly among maples, elms, and black ash.

behavior

These birds remain among the treetops most of the time, much to the chagrin of birders. They are always on the move, seldom staying still for more than a few minutes before moving to another perch. The birds sing throughout the day.

feeding ecology and diet

Insects.

reproductive biology

The cup-shaped, neat nest, which the bird builds high up in the trees, consists mostly of moss and lichens. The white to greenish white, speckled eggs usually number four, and they hatch in about two weeks.

conservation status

Although not threatened under IUCN criteria, cerulean warbler populations have declined by as much as 70% over the last three decades. The primary cause appears to be habitat destruction in both their breeding and wintering grounds. Efforts are currently under way to protect their northern and southern habitats.

significance to humans

They have some economic benefit, as they bring to the northern woods birders who are seeking a challenge in bird observation.

Resources

Books

Bent, Arthur C. Life Histories of North American Wood Warblers. New York: Dover Publications, Inc., 1963.

Cassidy, James, ed. Book of North American Birds. New York: The Reader's Digest Association, Inc., 1990.

Dock Jr., George. "Yellow-Breasted Chat." In Audubon's Birds of America. New York: Harry N. Abrams, Inc., 1979.

Ehrlich, Paul R., David S. Dobkin, and Darryl Wheye. The Birder's Handbook. New York: Simon and Schuster, Inc. (Fireside Books), 1988.

Garrett, Kimball L., and John B. Dunning Jr. "Wood-Warblers." In The Sibley Guide to Bird Life and Behavior, edited by Chris Elphick, John B. Dunning Jr., and David Allen Sibley. New York: Alfred A. Knopf, 2001.

Peterson, Roger Tory. A Field Guide to the Birds of Eastern and Central North America. Boston: Houghton Mifflin Co.,1980.

Periodicals

Berger, Cynthia. "Exposed: Secret Lives of Warblers." National Wildlife 23 (2000): 46–52.

Dunaief, Daniel. "Taking Back the Nest." Discover 16 (1995): 34.

Heist, Annette. "Singing in the Brain." Natural History 109, no. 8 (2000): 14–16.

Lichtenstein, G. and S. G. Sealy. "Nestling Competition, Rather Than Supernormal Stimulus, Explains the Success of Parasitic Brown-Headed Cowbird Chicks in Yellow Warbler Nests." Proceedings of the Royal Society of London B 265, no. 1392 (2000): 249–254.

Line, Les. "Tale of Two Warblers." National Wildlife 32 (1994): 16–19.

Lovette, I. J., and E. Bermingham. "Explosive Speciation in the New World Dendroica Warblers." Proceedings of the Royal Society of London B 266, no. 1429 (1999): 1629.

Nowicki, Stephen, Susan Peters, and Jeffrey Podos. "Song Learning, Early Nutrition, and Sexual Selection in Songbirds." American Zoologist 38, no. 1 (1998): 179–190.

Price, T., H. L. Gibbs, L. de Sousa, and A. D. Richman. "Different Timing of the Adaptive Radiations of North American and Asian Warblers." Proceedings of the Royal Society of London B 265 (1998): 1969–1975.

Raikow, Robert J. "Phylogeny and Evolution of the Passerine Birds." BioScience 50, no. 6 (2000): 487–499.

Sibley, C. G., and J. E. Ahlquist. "Reconstructing Bird Phylogeny by Comparing DNAs." Scientific American (Feb.1986): 82–92

Tangley, Laura. "A Good Place in the Sun: Tropical Winter Habitat Proves Critical to North America's Migratory Songbirds." U.S. News & World Report 125, no. 23 (1998):63.

Van Buskirk, J. "Independent Evolution of Song Structure and Note Structure in American Wood Warblers." Proceedings of the Royal Society of London B 264, no. 1382 (1997): 755–761.

Weidensaul, Scott. "Jewels in the Treetops." Country Journal 23 (1996): 58–61.

Yezerinac, M., and P. J. Weatherhead. "Extra-Pair Mating, Male Plumage Coloration, and Sexual Selection in Yellow Warblers (Dendroica petechia)." Proceedings of the Royal Society of London B 264, no. 1381 (1997): 527–532.

Organizations

National Audubon Society Population & Habitat Program. 1901 Pennsylvania Ave. NW, Suite 1100, Washington, DC 20006 USA. Phone: (202) 861-2242. E-mail: population@ audubon.org Web site: <http://www.audubonpopulation.org>

Smithsonian Migratory Bird Center, Smithsonian National Zoological Park. 3001 Connecticut Avenue, NW, Washington, DC 20008 USA. Phone: (202) 673-4800. E-mail: [email protected] Web site: <http://www.natzoo.si.edu>

The Songbird Foundation. 2367 Eastlake Ave. East, Seattle, WA 98102 USA. Phone: (206) 374-3674. Fax: (206) 374-3674. E-mail: [email protected] Web site: <http://www.songbird.org>

Other

"Threatened Animals of the World." Listing of at-risk species prepared by the UNEP World Conservation Monitoring Centre. (19 January 2002). <http://www.wcmc.org.uk/data/database/rl_anml_combo.html>

Leslie Ann Mertz, PhD