Black-throated Blue Warbler (Dendroica caerulescens)

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


Population Information

Federal BBS information can be obtained at by clicking on Trend Estimates and selecting the species in question. All estimates are for 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 Blue Warbler breeds primarily in large tracts of mature deciduous or mixed deciduous/coniferous forests with a well-developed understory (Holmes 1994). In Wisconsin it favors upland forests of maple or mixed northern hardwoods (Howe 2006). Robbins et al. (1989) listed this species as area-sensitive, occurring mainly in forest tracts >100 ha. Several authors have found Black-throated Blue Warblers to be tolerant of certain silvicultural systems. Jobes et al. (2004) found similar abundances in unharvested reference stands and stands subjected to recent selection cutting (1-5 years), but lower abundance in stands harvested 15-20 years prior. The significant increase in shrub density shortly after selection harvest likely contributed to the higher abundances. Harris and Reed (2002) documented a variety of responses to clearcut edge and forest interior sites, including some positive correlations to edge sites. Pairing success was higher near edges, where understory density was significantly greater. Furthermore, there was no apparent net difference in the probability that a male establishing a territory at an edge or interior site would produce fledglings. However, response to edge will vary depending on the landscape in which the edge is embedded.

Nests are placed in a dense understory of shrubs and saplings, usually within 1-1.5 meters of the ground. Doran and Holmes (2005) characterized high quality nesting sites as those with a greater proportion of deciduous vegetation and denser understory than surrounding sites. Within the contiguous forested landscape of this study, there was significant intraspecific spatial variation in bird abundance. The majority of individuals were found in relatively few locations across the landscape. Hoffman (unpubl. data) also documented a disproportionately high occupancy rate at one site in northern Wisconsin. Six territorial males were present within a 2-ha unsalvaged blowdown in old-growth forest.  

Habitat Availability

In Wisconsin the Black-throated Blue Warbler occurs primarily in the northern region of the state (Robbins 1991). Prior to Euro-American settlement, the northern mesic forest covered the largest acreage of any Wisconsin vegetation type. Today this forest type is still very extensive, but fragmentation of contiguous blocks and the simplification of forest structure and composition are concerns. Many mature and old-growth stands have been replaced by second-growth forests of aspen, white birch, sugar maple, and red maple (WDNR 2005).

Population Concerns

Breeding Bird Survey data suggest non-significant increases for this species; however, these results are difficult to interpret due to small sample sizes (Sauer et al. 2005). Contradictory results from the Nicolet National Forest Bird Survey (1987-2001) suggest significant population declines (Howe and Roberts 2005). Due to the rarity of the Black-throated Blue Warbler in Wisconsin, increased BBS coverage or targeted survey efforts are likely required to obtain a true assessment of its status. During the six-year period (1995-2000) of the Wisconsin Breeding Bird Atlas, observers confirmed breeding in just 2% of the surveyed quads (Howe 2006).

Limiting factors for the Black-throated Blue Warbler are poorly known. Wisconsin is near the western edge of this species’ breeding range (Robbins 1991), thus it has likely never been common within the state. Loss or fragmentation of large blocks of older, structurally complex forests may negatively impact this species. Overbrowsing by deer may suppress populations locally by reducing the shrub layer available for nesting (WDNR 2005). Loss of habitat on the wintering grounds in the West Indies also is suggested as a possible limiting factor (Holmes 1994).

Recommended Management

Management efforts for this species should focus on maintaining large blocks of mature forest with patches of vertical complexity (WDNR). Management practices that promote a well-developed shrub understory also will benefit this species. This includes providing canopy gaps through single tree and group selection harvest practices in northern hardwood stands (Jobes et al. 2004) and retaining balsam fir within managed stands.

Conservation and management strategies for this species should be focused in the following Wisconsin ecological landscapes: North Central Forest, Northern Highland, Northern Lake Michigan Coastal, and Superior Coastal Plain (WDNR 2005). Within these landscapes, key conservation sites include the Chequamegon-Nicolet National Forest in Ashland and Bayfield counties, Penokee Range IBA in Iron County, and Plum Lake Hemlock Forest State Natural Area in Vilas County. 

Research Needs

In Wisconsin, studies investigating the response to different silvicultural treatments would help guide future management efforts. Additionally, the potential impacts of deer browsing warrants study (WDNR 2005). Habitat-specific demography in the winter has not been adequately examined (Holmes 1994). More information is needed regarding the wintering distribution of specific populations.

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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