The Black-and-white Warbler is one of the most distinctive wood-warblers (Parulinae), yet its ecology has been surprisingly little studied. It is the only member of the genus Mniotilta (which means “moss-plucking,” a reference to the species' bark-foraging behavior). Its unique, sharply defined black-and-white striped plumage, evident in all seasons, accounts for its specific name, varia (meaning “variegated”).
This species has the unusual habit of methodically foraging on tree trunks and thick limbs, creeping along like a nuthatch and using its slightly decurved bill to probe among bark fibers—a behavior that has given it the common name of black-and-white creeping warbler, or simply black and white creeper. (It has also been called pied creeper, creeping warbler, striped warbler, whitepoll warbler, and scrannel.) Although it is the only North American wood-warbler that regularly forages on bark, it also routinely forages among foliage in a manner typical of most other foliage-gleaning wood-warblers. It tends to feed at mid-heights but may be observed anywhere from the canopy to the forest floor.
The Black-and-white Warbler is a common summer resident throughout most of the eastern and central United States and much of Canada and is a long-distance migrant. Its extensive wintering range includes most of Mexico and Central America, the Caribbean islands (West Indies and Bahamas), and northern South America, and during migration it is regularly recorded as a rarity along the Pacific Coast (a few winter in California) and as a vagrant in northern Europe, especially Britain and Ireland. Unlike many other neotropical migrants, this species does not show evidence of a general population decline, though it is clearly sensitive to forest fragmentation.
This is one of the earliest wood-warblers to return to its breeding grounds in spring. It inhabits open woodland, second growth, and mature forest, strongly favoring deciduous forest but also occurring in mixed deciduous and coniferous woods. It does not breed as commonly in spruce-fir forests but may be increasing in some boreal regions. Males arrive first on the breeding grounds, sing and defend territories, drive away conspecifics, and actively pursue females. Females are the principal nest-builders, constructing nests of dry leaves and grasses that are normally concealed on the ground at the base of a tree or fallen log. The prevalent song is easy to learn, a repetitive, high-pitched weesee.
On its wintering grounds this species is often found in disturbed habitats, forest edge, plantations, parks, and gardens, but it tends to be most abundant in interior forest. Individuals are territorial but nonetheless commonly join mixed foraging flocks that include neotropical resident species as well as other migrants.