Black-and-white Warbler

The black-and-white warbler (Mniotilta varia) is a strikingly patterned New World warbler, the sole representative of its genus. This diminutive bird, measuring between 11 cm (4.3 in) to 13 cm (5.1 in) in length and weighing 8 g (0.28 oz) to 15 g (0.53 oz), is cloaked in a bold black-and-white plumage. Both sexes boast a black and white crown, a white eyebrow, and black streaking on a white belly. Their wings are adorned with two white bars, and their backs are a tapestry of black-and-white streaks. Males, during the breeding season, are distinguished by a streaked throat and black cheek, while females exhibit a grey cheek with a lighter throat and sides. Juveniles and first fall individuals are heavily spotted and less streaked than adults.

Identification Tips

When identifying the black-and-white warbler, look for its unique black-and-white striped pattern, which is reminiscent of a zebra. The male's breeding plumage is particularly bold, with stark black-and-white streaking. The bird's behavior of creeping along tree trunks and branches is also a key identification feature, setting it apart from other warblers. It can be confused with the blackpoll warbler, which has a solid black cap, or behaviorally with the pine warbler and yellow-throated warbler.

Habitat

The black-and-white warbler is versatile in its habitat preferences. During the breeding season, it favors mature deciduous and mixed forests, including swampy areas. It is less particular outside of the breeding season, occupying a range of habitats from mangroves to various forest types, and even adapting to human-modified landscapes like shade coffee plantations and gardens.

Distribution

This migratory warbler breeds across northern and eastern North America, from the Northwest Territories and Newfoundland to North Carolina and Texas. Come winter, it travels to Florida, Central America, the West Indies, and as far south as Peru. It is an occasional vagrant to western Europe.

Behaviour

The black-and-white warbler is a territorial bird, defending its breeding and wintering grounds with vigor. It exhibits a unique foraging behavior, reminiscent of nuthatches, as it probes tree bark for insects. During migration, it may join mixed-species flocks for feeding.

Song & Calls

The song of the black-and-white warbler is a high-pitched series of "wee-see" notes, often repeated in quick succession. It also has a distinctive "chip" call and a softer "seet-seet" call that may be heard during flight.

Breeding

This warbler nests on the ground, often in damp areas, constructing a cup nest where it lays 4-5 eggs. The female incubates the eggs, and both parents tend to the young. The species is known to produce one brood per year and may fall victim to brood parasitism by the brown-headed cowbird.

Diet and Feeding

The black-and-white warbler's diet consists primarily of insects and spiders. Its foraging technique is unique among warblers, as it moves along tree trunks and branches, probing for prey beneath the bark. It is adapted to this feeding style with short legs and a long hind toe.

Conservation status

The IUCN lists the black-and-white warbler as Least Concern, though its population is on the decline. Habitat loss and fragmentation, particularly in its breeding grounds, are the main threats to its survival. Past use of pesticides has also contributed to population declines.