Mniotilta varia

Geographic Range

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.

• Biogeographic Regions
• nearctic nearctic
  • native native
• neotropical neotropical
  • native native

Habitat

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.

• Habitat Regions
• temperate temperate
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• rainforest rainforest

Physical Description

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 .

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

Mniotilta varia is most likely monogamous.

• Mating System
• monogamous monogamous

Mniotilta varia is one of the first warblers to arrive in the spring. There is some evidence that it will return to the same territories in successive years. Preferred breeding habitat includes deciduous and deciduous-conifer forests, especially on hillsides, in ravines and swampy forests.

Mniotilta varia typically breeds between April and August. Males arrive first in the spring. Soon after arriving, they set up territories and begin courting a mate. The courting male pursues the female intermittently over a long period of time, with much song and display of plumage. After pursuing the female, the male will perch near the female with fluttering wings.

The female is the principal nest builder. The nest is a cup, generally on the ground at the base of a tree or fallen log and concealed under dead leaves or branches. The nest is made of leaves, coarse grass, and other fine materials used for lining.

The female lays 4 to 6 (usually 5) white eggs that are flecked with brown and 16 to 18 mm long. Incubation, completed by the female only, takes 10 to 12 days. The male sometimes feeds the incubating female. Both parents feed the young and defend the nest. The young leave the nest 8 to 12 days after hatching. They remain in the parents' territory for 2 to 3 weeks after fledging. Generally there is only one brood per year, although two broods per year is possible.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

Mniotilta varia breeding pairs share parental responsibilities. The female builds the nest and incubates the eggs. Both parents feed the young and defend the nest.

• Parental Investment
• altricial altricial
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
• pre-weaning/fledging

Lifespan/Longevity

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

Behavior

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.

• Key Behaviors
• terricolous
• flies
• diurnal diurnal
• motile motile
• migratory migratory
• territorial territorial

Home Range

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

Communication and Perception

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.

• Communication Channels
• visual visual
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

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.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore

• Animal Foods
• insects
• terrestrial non-insect arthropods

Predation

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 .

Ecosystem Roles

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.

Economic Importance for Humans: Positive

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

Economic Importance for Humans: Negative

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

Conservation Status

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.

Other Comments

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.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Kari Kirschbaum (author, editor), Animal Diversity Web.

Jacob Foster (author), University of Michigan-Ann Arbor, Terry Root (editor), University of Michigan-Ann Arbor.

References

Anderson, K., H. Maxfield. 1967. Warbler returns from southeastern Massachusetts. Bird Banding , 43: 218-233.

Blake, C., J. Cadbury. 1969. An old warbler. Bird Banding , 40: 255.

Burtt, E. 1980. Overwing and underwing head scratching by a male Black-and-white Warbler (Mniotilta varia). Ibis , 122: 541.

Dunn, J., K. Garrett. 1997. A field guide to warblers of North America. Peterson Field Guide Series . NY: Houghton Mifflin Co.

Ehrlich, P., D. Dobkin, D. Wheye. 1988. The birder's handbook: A field guide to the natural history of North American birds . NY: Simon & Schuster Inc.

Kricher, J. 1995. Black-and-white Warbler ( Mniotilta varia ). Pp. 1-20 in The Birds of North America , Vol. 158. Philadelphia, PA: The Academy of Natural Sciences, and Washington DC: The American Ornithologists' Union.