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    Black-and-white Warbler Life History

    Habitat

    Habitat ForestsBlack-and-white Warblers typically use deciduous forests and mixed forests of deciduous trees and conifers. They can be found in many habitats during migration, especially woodlots and forests in riparian settings. On their tropical wintering grounds Black-and-white Warblers use an immense range of habitats, including lawns, gardens, and other urban settings, fruit orchards, shade-coffee plantations, wetlands, mangroves, and all types of forests.Back to top

    Food

    Food InsectsBlack-and-white Warblers eat mostly insects. Moth and butterfly larvae form the bulk of their diet during spring migration and throughout the breeding season. Other arthropod prey includes ants, flies, spiders, click and leaf beetles, wood-borers, leafhoppers, and weevils. They also feed on insects attracted to Yellow-Bellied Sapsucker sapwells. Back to top

    Nesting

    Nest Placement

    Nest GroundThe female Black-and-white Warbler selects a well-hidden nesting location at the base of a tree, rock, stump, or fallen log, or under a bush or shrub. Nests are usually built on the ground but occasionally are placed in a cavity atop a tree stump, in a rock crevice, or on a mossy bank up to six feet high.

    Nest Description

    The round, open cup-shaped nest is constructed from dry leaves, bark strips, grass, and pine needles, reaching just over 5 inches in diameter and 5 inches high. The nest cup, which measures up to 3 inches in diameter and 2.5 inches high, is lined with moss, horsehair, and dried grasses.

    Nesting Facts
    Clutch Size:4-6 eggs
    Number of Broods:1-2 broods
    Egg Length:0.6-0.8 in (1.5-1.9 cm)
    Egg Width:0.5-0.6 in (1.3-1.4 cm)
    Incubation Period:10-12 days
    Nestling Period:8-12 days
    Egg Description:Creamy white, pale bluish- or greenish-white, with speckles of brown or lavender.
    Condition at Hatching:Helpless, with pink skin and dark gray down.
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    Behavior

    Behavior Bark ForagerBlack-and-white Warblers crawl along tree trunks and thick limbs as they probe methodically between bark fibers for grubs and insects. Unlike Brown Creepers, which tend to move up a tree as they feed, or nuthatches, which typically move downward, this warbler moves in every direction. They forage on dead limbs and bark as well as gleaning foliage at the tips of branches. Male Black-and-white Warblers arrive in early spring on their forested breeding grounds and set up territories that they defend aggressively, often singing as they chase off intruders. These defensive displays extend well past the time when such behavior has tapered off for other species. A courting male chases potential mates on his territory, perching nearby and fluttering his wings. Once the pair is established, the female leads her partner to likely nest spots at the base of a tree or fallen log, and takes the lead in constructing the well-camouflaged nest.Back to top

    Conservation

    Conservation Low ConcernBlack-and-white Warblers are common, although populations declined by about 33% between 1966 and 2014, according to the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population at 20 million, with 25% spending some part of the year in the U.S., 75% breeding in Canada, and 43% wintering in Mexico. They rate a 10 out of 20 on the Continental Concern Score and is not on the 2014 State of the Birds Watch List. In the past, Black-and-white Warblers have proven susceptible to persistent organic pesticides used to combat insects. Today, the main concern for this forest-interior species is fragmentation of forests into smaller and smaller parcels. Like many nocturnal migrants, Black-and-white Warblers are vulnerable to collisions with tall buildings and radio towers.Back to top

    Credits

    Kricher, John C. 2014. Black-and-white Warbler (Mniotilta varia), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

    Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

    North American Bird Conservation Initiative. 2014. The State of the Birds 2014 Report. US Department of Interior, Washington, DC, USA.

    Partners in Flight. 2017. Avian Conservation Assessment Database. 2017.

    Sauer, J. R., J. E. Hines, J. E. Fallon, K. L. Pardieck, Jr. Ziolkowski, D. J. and W. A. Link. The North American Breeding Bird Survey, results and analysis 1966-2013 (Version 1.30.15). USGS Patuxtent Wildlife Research Center 2014b. Available from http://www.mbr-pwrc.usgs.gov/bbs/.

    Sibley, David Allen. 2014. The Sibley guide to birds, second edition. Alfred A Knopf, New York.

    Stephenson, Tom and Scott Whittle. 2013. The Warbler Guide: Princeton University Press.

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