The black-and-white warbler (Mniotilta varia) is a small songbird of the New World warbler family Parulidae. These birds breed in northern North America and spend the winters in southern North America, Central America, and the Caribbean islands. They are a fairly common sight in woodlands and gardens during migration. Black-and-white warblers display some key identifying features including plumage coloration, vocalizations, habitat preferences, diet, and behaviors. Read on to learn more about the characteristics that distinguish these widespread yet striking warblers.
Appearance
The breeding adult male black-and-white warbler displays black and white plumage that gives this bird its common name. The upperparts are mostly black with white spotting on the wings and white stripes down the back. The underparts are white with black streaking on the breast and flanks. The black-and-white pattern is a distinctive field mark of an adult male. Females display more muted plumage overall with gray streaking in places of the male’s black plumage. Immature birds in their first spring resemble adult females.
This warbler has a relatively long, thin and pointed bill suited to probing bark crevices for insects. Their legs are also long and slender compared to many other warblers. Black-and-white warblers are very active foragers, rather acrobatic as they creep along branches and tree trunks searching for insects. They measure 11–13 cm in length and have a wingspan of 17–21 cm. Body mass ranges from 7 to 12 g.
Plumage Details
Here are some more specifics on the black-and-white warbler’s distinctive plumage:
- Crown is black with white streaks
- Black stripe runs through the eye
- Thin white ring around the eye
- Back is mostly black with thick white stripes
- Upper tail is black with white tips
- Undertail is white with black tips
- Breast is white with black streaking
- Belly and undertail coverts are clean white
- Wings are black with two white wing bars
- Long, thin black bill and legs
The plumage of females is less contrasting overall with gray replacing some of the black markings. Immature birds in their first year resemble adult females.
Song and Calls
The song of the black-and-white warbler is a very high-pitched, buzzy trill described as “weesy, weesy, weesy.” Their call is a distinctive “chip.” These vocalizations are often the easiest way to identify this warbler as it moves quickly through branches and foliage.
Males sing persistently from high perches in the spring to attract females and defend territory. Their trilled songs carry well through the woods. Females may also sing, but less frequently than males during the breeding season.
Song Audio
Here is an audio clip of the black-and-white warbler’s song:
The staccato trilling is a signature sound of the species. Listen for this very high-pitched song in deciduous woods during spring and summer.
Habitat
Black-and-white warblers breed in mature, deciduous and mixed forests across North America. They prefer large tracts of forest with a dense understory. They often inhabit floodplain forests along rivers and wetland margins.
During migration, these warblers can be found in a wider variety of wooded habitats including younger second-growth forests. They are adaptable to human-altered landscapes when traveling between their breeding and wintering grounds.
On their wintering grounds, black-and-white warblers occupy a range of wooded tropical habitats including mangroves, pine-oak forests, shade coffee plantations, and gardens.
Breeding Habitat Types
Here are some examples of specific habitat types favored by black-and-white warblers for breeding:
- Floodplain forests
- Swamp peripheries
- Mature upland deciduous forest
- Northern hardwood forests
- Old mixed forests with conifers
- Dense second-growth woodlands
Availability of mature, humid forests with plenty of understory is a key habitat requirement for successful breeding.
Food and Foraging
The diet of black-and-white warblers consists predominantly of insects and other small invertebrates. This includes caterpillars, beetles, ants, spiders, flies, and insect eggs. They also occasionally eat nectar from flowers.
These birds forage actively throughout trees searching for insect prey. Their foraging style is distinctive, creeping along branches and climbing up tree trunks rather than making short hops and flights like many warblers. They have a particular way of circling around on branches and trunks that has been described as reminiscent of nuthatches. Their long hind claws are an adaptation to clinging securely to bark.
Black-and-white warblers use their thin, pointed bill to pick and probe for insects hiding in crevices in the bark. They move quickly and scrutiny while foraging, covering a lot of ground. They make frequent fly-catching sallies from perches to hawk insects out of the air as well.
Insect Type | Examples |
---|---|
Caterpillars | Moth, butterfly larvae |
Beetles | Weevils, leaf beetles |
Flies | Midges, gnats |
Spiders | Orb weavers, crab spiders |
Ants | Various species |
Migration
The black-and-white warbler is migratory, breeding across Canada and the northern United States before traveling to southern North America for the winter. They are among the first warblers to arrive on breeding grounds in spring, often setting up territories in late April or early May. Males arrive a few days ahead of females.
Fall migration back to the wintering grounds begins in August, peaking in September. They are one of the last warbler species to complete their southern journey in late October.
These warblers migrate primarily at night. They travel overland through North America rather than taking long overseas flights across the Caribbean like some other warbler species. Migration routes center on several main flyways through the Great Lakes, Mississippi River Valley, and Appalachian regions.
Approximate Migration Timeline
- Spring arrival on breeding grounds: April to early May
- Fall departure from breeding grounds: Mid-August to early September
- Peak of southbound migration: Mid-September
- Arrival on wintering grounds: Late September to late October
The exact timing varies across their breeding and wintering ranges.
Breeding and Reproduction
Black-and-white warblers breed in mature, deciduous and mixed forests across Canada and the northeastern to upper Midwestern United States. Courtship begins shortly after spring arrival when males sing persistently to attract mates and defend nesting territories.
These warblers are predominantly monogamous. Pairs work together to build the nest on the ground concealed among dead leaves, ferns, or other dense understory vegetation. The female lays 3-7 eggs which she incubates for 11-12 days while the male feeds her. Both parents feed the nestlings.
The chicks fledge the nest at 8-12 days old but remain dependent on parental care for a few more weeks. Most pairs raise one brood per season. Nest predation by snakes, chipmunks, and other animals is a common cause of nest failure. Brown-headed cowbirds may sometimes lay eggs in warbler nests.
Breeding Stage | Approximate Timeframe |
---|---|
Nest Building | Late April to Mid-May |
Egg Laying | May to early June |
Incubation | 11-12 days |
Nestling Period | 8-12 days |
Fledging | Late May to mid-June |
The exact breeding timeline varies across their range. Most breeding activity occurs from mid-May through early July.
Conservation Status
Black-and-white warblers have a large breeding distribution across North America. Partners in Flight estimates a global breeding population of 67 million with 79% spending some part of the year in the United States. They are currently listed as Least Concern on the IUCN Red List due to their large range and stable population trends.
These birds do face threats from habitat loss as mature forests are logged and flooded on their breeding grounds. Pesticide use also reduces their insect food supplies. But overall, black-and-white warbler populations appear secure for now barring major habitat changes in the future. Maintaining healthy, undisturbed forests across North America is important for the continued success of these colorful warblers.
Fun Facts
Here are a few interesting tidbits of information about the black-and-white warbler:
- They get almost all of their food by gleaning insects from tree bark rather than catching them in flight.
- They are the only warbler species that regularly creeps and climbs along tree trunks to forage.
- They have specially adapted hind claws that allow them to cling to bark.
- Their sharp, pointed bill helps them probe into crevices in the bark.
- They are one of the earliest migrating warblers in spring.
- They often reuse the same nesting territory year after year.
- The male’s loud song is used to attract females and defend territory.
- Nests are built completely by the female and hidden on the forest floor.
Conclusion
In summary, the black-and-white warbler is a strikingly patterned songbird best identified by its namesake plumage, buzzy trilled song, and unique foraging behavior on tree trunks. They breed in mature forests across Canada and the northern United States before migrating to wintering grounds in the southern U.S., Mexico, and Caribbean. Though relatively common, conservation of their breeding habitat is important for this species. The black-and-white warbler stands out for both its appearance and habits among the diverse North American wood-warblers.