Black-throated Green Warbler (Dendroica virens)

Photo by Dennis MaluegBlack-throated Green Warbler by Dennis MaluegBlack-throated Green Warbler distribution map


Population Information

The Federal BBS information can be obtained at by clicking on Trend Estimates and selecting the species in question. All estimates are for time period (1966-2005).

*Note: There are important deficiencies with these data. These results may be compromised by small sample size, low relative abundance on survey route, imprecise trends, and/or missing data. Caution should be used when evaluating this trend.

Life History

Habitat Selection

The Black-throated Green Warbler is found nesting in boreal and mixed northern forests in a wide variety of forest habitat types (Robbins 1991). It likely reaches its highest abundance in older mixed northern hardwood-hemlock stands. Nests are placed in conifers at the point where two branches emerge from the trunk of a tree. The majority of nests are within 1-3 (3-10 feet) meters above ground, but this species sometimes nests as high as 20 meters (65 feet) above ground (Morse 1993).

This species is segregated by sex in terms of habitat preference on the wintering grounds in Mexico (Lopez Ornat and Greenberg 1990) .

Habitat Availability

The Black-throated Green Warbler chooses a variety of forest habitats in WI, being found in white cedar swamps (Hoffman and Mossman 1993), extensive northern alder thickets with associated swamp conifers (Hoffman 1989b), boreal forests (Mossman et al. 1990), pine forests (Hoffman and Mossman 1990), and northern mesic forests (Hoffman 1989a). Most northern forest types in WI therefore have this species present, and it is considered a “source/core” species (Howe et al. 1992), with individuals from WI sustaining global populations by providing surplus individuals that move to other geographic areas.

Population Concerns

This species has shown periodic declines in some areas of its range (WI and MI), while other areas (northern MN, for example) have shown stable populations (Morse 1993). However; recent data suggests that BTNW are increasing in WI. Year-to-year variation in numbers is noticeable, perhaps in response to unfavorable weather conditions in some breeding seasons. Blake et al. (1992) studied response of this species to drought, and hypothesized that drought may be responsible for periodic declines in WI. Numerous studies show this species is sensitive to forest fragmentation (Askins 2000, Rappole 1995). This species will disappear from areas after intensive even-aged logging of both coniferous and deciduous forests, especially if remaining forest stands are isolated. The Black-throated Green Warbler declines sharply after the application of pesticides to control for spruce-budworm infestations. The BTNW is negatively impacted by forest cutting on the wintering grounds, but it will use canopy tree species in coffee plantations. Because of its large winter range, it may not be as susceptible to localized forest removal in the tropics as some other passerines (Chequamegon NF Bird Survey (NRRI) species account, Morse 1993).

Partners in Flight categorizes this species as a continental stewardship and regional stewardship species for Wisconsin. Wisconsin and the other Western Great Lakes states have a long-term planning responsibility to ensure continued healthy source populations across the region.

Recommended Management

Pearson and Niemi (2000) determined that management of forests for these species requires the maintenance of conifer components within the forests of northern MN, and we have every reason to expect the same is true for northern WI. They state that conifer stands may support “source populations” of these species, from which some individuals may then move into nearby deciduous forest habitats. This indicates a need for “landscape-level” management, protecting both deciduous and coniferous forest habitats, to provide for a diversity of species (Pearson and Niemi 2000). Howe et al. (1992) described BTNW as a “source/core” species, which is in agreement with Pearson and Niemi’s recommendations. BTNW was one species in a study by Darveau et al.(1995) that was present in 60-meter-wide riparian strips left after logging, but not in 20- meter-wide strips. Morrison et al. (1998) suggest this may mean wider riparian strips provided after logging may provide a good riparian buffer width for conservation of forest birds, but the authors mention that data are needed on demographics of these species (BTNW, Swainson’s Thrush, Golden-crowned Kinglet) after this type of forest treatment. In general, uneven-aged management of mesic forest types that promote conifer retention should benefit this species.

Research Needs

Continued research into population regulation of this and other Neotropical migrants is needed. A complicated set of factors (incl. deforestation on both breeding and wintering grounds, long-term effects of pesticides on populations, effects of habitat fragmentation on breeding grounds, aftereffects of extreme weather events) may variably affect numbers across the geographic range of the Black-throated Green Warbler and its congeners (Morse 1993).

Information Sources


Contact Information

Kreitinger, K., Y. Steele and A. Paulios, editors. 2013.
The Wisconsin All-bird Conservation Plan, Version 2.0. Wisconsin Bird Conservation Initiative.
Wisconsin Department of Natural Resources. Madison, WI.

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