What do they look like?

Black-and-white warblers are small birds that are black and white all over. They have a black crown with bright white stripes behind each eye, a black-and-white back, and a grayish tail with white spots at the corners. They weigh 9 to 15 g and are 11 to 13 cm long. Black and white warblers have a long back claw on each short leg. These help them to climb around on branches and trunks. Their bills curve slightly downward. This shape helps them when they are probing in bark and mosses for food.

Male and female black-and-white warblers look very similar. Females are usually a little bit smaller than males.

Where in the world do they live?

Black-and-white warblers breed throughout the eastern United States and much of Canada. They spend the winter in southern Florida, Mexico, Central America, the Caribbean Islands and northern South America.

What kind of habitat do they need?

Black-and-white warblers breed in deciduous and mixed deciduous-conifer forests. They prefer forests with large trees and an understory of smaller trees and shrubs. In winter, black-and-white warblers can be found in a variety of forest types, as well as woodland borders, gardens, and coffee plantations.

How do they reproduce?

Black-and-white warblers are probably monogamous.

Black-and-white warblers breed between April and August. Males arrive first in the spring. Soon after arriving, they establish a territory, and then begin looking for a mate. The males try to attract a female by following her around, singing and showing off their feathers. They may also perch near the female and flutter their wings.

Once a pair has formed, the female builds the nest. The nest is cup-shaped, and is made of leaves and grasses. Nests are built on the ground at the base of a tree or next to a fallen log. They are usually hidden under dead leaves or branches.

When the nest is finished, the female lays 4 to 6 (usually 5) white eggs with brown flecks. She incubates them for 10 to 12 days. The male sometimes brings food to the female while she is incubating. After the chicks hatch, both parents feed them and defend the nest. The chicks leave the nest after 8 to 12 days. They stay in their parents' territory for 2 to 3 weeks before leaving.

Most black-and-white warblers raise one brood per year. However, some breeding pairs are able to raise two broods per summer.

Both male and female black-and-white warblers take care of their young. The female builds the nest and incubates the eggs. After the chicks hatch, both parents feed and protect them.

How long do they live?

The oldest known black-and-white warbler lived at least 11 years. Most black-and-white warblers probably do not live nearly this long.

How do they behave?

Black-and-white warblers are diurnal (active during the day). They are also migratory. All black-and-white warblers migrate in the spring and fall.

Black-and-white warblers are territorial. They defend territories during the breeding season and sometimes in the winter too. During migration and winter, black-and-white warblers are more social. They often join feeding flocks with other bird species.

Home Range

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

How do they communicate with each other?

Black-and-white warblers use calls and body signals to communicate. The songs of black-and-white warblers are high-pitched and squeaky. The most common song sounds like wee-see repeated 6 to 10 times. It can last up to 3 seconds. To some people, this song sounds like a squeaky wheel. Black-and-white warblers also use call notes, like chip and tik to communicate.

What do they eat?

Black-and-white warblers are insectivores. They mostly eat insects that they find on the trunks and limbs of trees. Common foods that black-and-white warblers eat include caterpillars, flies, bugs, beetles, borers, spiders, larvae, and egg masses.

Black-and-white warblers are the only wood-warblers that forage for most of their food on bark. They creep along branches and trunks from the ground up to the canopy, picking and probing into cracks and crevices with their bills. They even hang on the undersides of branches and creep down tree trunks head-first. Because black-and-white warblers find most of their food in tree trunks, they don't have to wait for insects to emerge in the spring. This means that they can arrive at the breeding grounds earlier in the spring than other warblers. Black-and-white warblers sometimes forage by catching insects in the air and searching for them amongst leaves.

What eats them and how do they avoid being eaten?

There is not much information available about predation of black-and-white warblers. As a ground nesting species, black-and-white warblers are probably vulnerable to many different predators, especially during the breeding season. Common forest animals such as blue jays, deer mice, eastern chipmunks, northern flying squirrels, red squirrels, raccoons and black bears are likely to be predators of black-and-white warblers.

What roles do they have in the ecosystem?

Black-and-white warblers affect the populations of insects they eat. They also provide food for their predators. Finally, they are habitat for parasites such as feather mites, lice and blood parasites.

Do they cause problems?

We do not know of any way that black-and-white warblers harm humans.

How do they interact with us?

We do not know of any way that black-and-white warblers affect humans.

Are they endangered?

Black-and-white warblers are a fairly common forest bird. There are about 14,000,000 black-and-white warblers across their range. Black-and-white warblers prefer large areas of forest. One of the major threats facing them is forest fragmentation. Other things that may harm black-and-white warblers include nest parasitism by cowbirds and pesticide poisoning.

Black-and-white warblers are not threatened or endangered. They are protected under the U.S. Migratory Bird Act.

Contributors

Jacob Foster, University of Michigan

Terry Root, University of Michigan

Contributors

Kari Kirschbaum, Animal Diversity Web Staff

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 A. Poole, F. Gill, eds. The Birds of North America, Vol. 158. Philadelphia, PA: The Academy of Natural Sciences, and Washington DC: The American Ornithologists' Union.