Mniotilta varia
black-and-white warbler

Mniotilta varia breeds throughout the eastern United States and much of Canada. Boreal areas through central and eastern Canada, from northeastern British Columbia east to Newfoundland and Labrador, make up its northern range. In the United States, Mniotilta varia breeds along the east coast from Maine, through New York, south to North Carolina and western South Carolina, and west to parts of Alabama and Mississippi. Mniotilta varia does not breed in the Mississippi River valley, but does breed as far west as eastern Texas and Oklahoma. In the midwest, M. varia breeds in northern portions of Michigan, Wisconsin, and Minnesota. This warbler winters from southern Florida through the Bahamas, Mexico, Central America, and the Caribbean to northern South America. (Dunn and Garrett, 1997; Ehrlich, Dobkin, and Wheye, 1988)

Mniotilta varia breeds in mature and second-growth deciduous and deciduous-conifer forests, favoring deciduous habitats. Large trees are a critical component of the habitat M. varia prefers. There are generally understory and ground-cover plants, tangles, and dead leaves for nest concealment. Mniotilta varia winters in a variety of forests from high-elevation cloud forests to lowland evergreen and deciduous forests, woodland borders, gardens, and coffee plantations. (Dunn and Garrett, 1997; Ehrlich, Dobkin, and Wheye, 1988)

Mniotilta varia is entirely black and white in all plumages, except for a creamy wash on the face and flanks of many females. The head has a white median crown stripe bordered by black. A bold white border to the tertials is distinctive, as are the black uppertail coverts with white fringes. The black-and-white striped crown and back are distinctive in all plumages. Mniotilta varia averages 11 to 13 cm long, although females are generally smaller than males. It has a mass of 9 to 15 g. Mniotilta varia has an elongated hind claw, shortened tarsi, and a long thin bill with a slightly curved culmen. These modifications allow M. varia to forage on tree trunks and branches in a manner similar to nuthatches. (Dunn and Garrett, 1997; Kricher, 1995)

The oldest known black-and-white warbler lived at least 11 years. One study estimated annual adult survivorship to be 71%. ()

Mniotilta varia is diurnal and migratory. It is also generally solitary, although it joins mixed-species flocks in winter and during migration.

Mniotilta varia is territorial and defends its space through aggression toward conspecifics and other wood-warblers. Aggressive behavior is often maintained beyond the time when other wood-warblers have ceased being aggressive. Males will sing while driving other birds from their territory. Females will flush and perform a distraction display if disrupted on the nest. (Burtt, 1980; Dunn and Garrett, 1997; Ehrlich, Dobkin, and Wheye, 1988; Kricher, 1995)

Home Range

The home range of black-and-white warblers is unknown.

Mniotilta varia communicates via vocalizations and physical displays. The song of M. varia is a lengthy (up to 3 seconds) series of thin, squeaky, very high-pitched notes (said to sound like wee-see) in a series of 6 to 10 phrases. It is distinguished from other high-pitched warbler songs by the chanting rhythm and the absence of a complex ending. A second longer, more varied, but less common song is sometimes given in flight. Calls include a dull chip or tik, as well as a doubled seet-seet (sometimes singe) flight call. (Dunn and Garrett, 1997)

Mniotilta varia primarily eats insects that are gleaned from trunks and limbs of trees in a very similar manner to nuthatches. Its main food items include caterpillars, flies, bugs, beetles, borers, spiders, larvae, and egg masses. It is the only North American wood-warbler that regularly forages on bark.

Mniotilta varia creeps along branches and trunks from the canopy to the ground, picking and probing with its thin bill. It often creeps upside-down along the undersides of branches, and may creep downward headfirst. By foraging from bark in this manner, M. varia can glean enough food (including dormant insect forms) before trees leaf out to allow it to arrive at its breeding grounds earlier than other warblers. Though it specializes in bark gleaning, Mniotilta varia also makes use of other foraging behaviors more typical of warblers, including occasional flycatching and foliage gleaning. (Dunn and Garrett, 1997; Ehrlich, Dobkin, and Wheye, 1988; Kricher, 1995)

Little information is available about predation of Mniotilta varia. As a ground nesting species, M. tilta is probably vulnerable to predation by a wide variety of predators, particularly during the breeding season. Probable nest predators include common forest bird and mammal species such as blue jays, deer mice, eastern chipmunks, northern flying squirrels, red squirrels, raccoons and black bears. (Ehrlich, Dobkin, and Wheye, 1988)

Mniotilta varia affects the populations of insects it eats. It also provides food for its predators. Finally, M. tilta hosts external and internal parasites, including feather mites, lice and blood parasites. (Ehrlich, Dobkin, and Wheye, 1988)

There are no known negative effects of Mniotilta varia on humans.

We do not know of any way that Mniotilta varia affects humans.

Mniotilta varia is very sensitive to fragmentation of forested breeding habitat. Populations of Mniotilta varia have been increasing as forests have regenerated after massive 19th century deforestation. The worldwide population of Mniotilta varia is estimated at about 14,000,000 individuals. Regional declines have occurred where forest fragmentation is again occurring. These declines may be compounded by cowbird parasitism, of which M. varia is a frequent host. There is also evidence that pesticide use has had a negative effect on M. varia populations.

Mniotilta varia is not threatened or endangered. It is, however, protected under the U.S. Migratory Bird Act. (Dunn and Garrett, 1997; Ehrlich, Dobkin, and Wheye, 1988; Kricher, 1995)

The scientific name Mniotilta varia derives from the unique bark-foraging behavior (Mniotilta refers to "moss-plucking") and the unique plumage evident in all seasons (varia refers to "variegated"). No subspecies are presently recognized. (Kricher, 1995)