A denizen of the forest interior, the Black-throated Blue Warbler inhabits large tracts of relatively undisturbed hardwood and mixed deciduous-coniferous forests in the northeastern United States and southern Canada, and south at higher elevations of the Appalachian Mountains to northern Georgia. Most individuals migrate along the eastern seaboard from the Appalachians to the Atlantic coast, and overwinter in forested habitats of the Greater Antilles from Puerto Rico to Cuba, Jamaica, and Hispaniola, with some in the Bahamas, along the coast of the Yucatan and Belize, and a few in south Florida.

Males and females of this species differ strikingly in appearance, and were even considered separate species by early naturalists, including Alexander Wilson ( Wilson, A. (1810). American ornithology or the natural history of birds of the United States. Vol. 2. Philadelphia, PA: Bradford and Inskeep. Close Wilson 1810) and John James Audubon ( Audubon, J. J. (1841). The birds of America, from drawings made in the United States and their territories. Vol. 3. Philadelphia, PA: J. J. Audubon. Close Audubon 1841). Males are unmistakable in their blue, black, and white plumage, while females are a more cryptic greenish-gray in color. This is one of the parulid warblers that does not molt into a “confusing fall plumage,” so individuals can be identified easily year-round. Populations differ somewhat in plumage, notably in the amount of dark streaking on the crown, dorsal feathers, and the size of white patches in wings—characters once used to separate the two subspecies.

Being a bird of forested landscapes, the Black-throated Blue Warbler likely experienced population declines when eastern North America was deforested and settled by Europeans in the 18^th and 19^th centuries ( Whitney, G. G. (1994). From coastal wilderness to fruited plain: a history of environmental change in temperate North America from 1500 to the present. New York: Cambridge Univ. Press. Close Whitney 1994). As fields and pastures in the heart of its range returned to forest mostly in the 20^th century, its populations probably increased throughout the region. In the future, however, changes in the quality of its breeding habitat ( Sillett, T. S., R. T. Holmes and T. W. Sherry. (2000). Impacts of a global climate cycle on population dynamics of a migratory songbird. Science 288:2040-2042. Close Sillett et al. 2000, Rodenhouse, N. L., T. S. Sillett, P. J. Doran and R. T. Holmes. (2003). Multiple density-dependence mechanisms regulate a migratory bird population during the breeding season. Proc. R. Soc. Lond. B. 270:2105-2110. Close Rodenhouse et al. 2003, Sillett, T. S. and R. T. Holmes. (2005). "Long-term demographic trends, limiting factors, and the strength of density dependence in a breeding population of a migratory songbird." In Birds of Two Worlds: Advances in the Ecology and Evolution of Temperate-Tropical Migration Systems., edited by R. Greenberg and P. P. Marra, 426-436. Baltimore, MD: Johns Hopkins University Press. Close Sillett and Holmes 2005, Holmes, R. T. (2011). Avian population and community processes in forest ecosystems: Long-term research in the Hubbard Brook Experimental Forest. Forest Ecology and Management 262 (1):20-32. Close Holmes 2011), overwintering habitat ( Holmes, R. T. (2007). Understanding population change in migratory songbirds: Long-term and experimental studies of Neotropical migrants in breeding and wintering areas. Ibis 149 (2):2-13. Close Holmes 2007, see also Studds, C. E. and P. P. Marra. (2007). Linking fluctuations in rainfall to nonbreeding season performance in a long-distance migratory bird, Setophaga ruticilla. Climate Research 35 (1-2):115-122. Close Studds and Marra 2007, Studds, C. E. and P. P. Marra. (2011). Rainfall-induced changes in food availability modify the spring departure programme of a migratory bird. Proceedings of the Royal Society B-Biological Sciences 278 (1723):3437-3443. Close Studds and Marra 2011), and enhanced risks during migration ( Sillett, T. S. and R. T. Holmes. (2002). Variation in survivorship of a migratory songbird throughout its annual cycle. J. Anim. Ecol. 71:296-308. Close Sillett and Holmes 2002) could reverse that trend. Climate change is another factor potentially affecting the distribution and abundance of this species ( Matthews, S. N., L. R. Iverson, A. M. Prasad and M. P. Peters. (2011). Changes in potential habitat of 147 North American breeding bird species in response to redistribution of trees and climate following predicted climate change. Ecography 34 (6):933-945. Close Matthews et al. 2011), but thus far, the species seems able to adjust to warming temperatures ( Kaiser, S. A., T. S. Sillett and M. S. Webster. (2014). Phenotypic plasticity in hormonal and behavioural responses to changes in resource conditions in a migratory songbird. Animal Behaviour 96:19-29. Close Kaiser et al. 2014, Townsend, A. K., T. S. Sillett, N. K. Lany, S. A. Kaiser, N. L. Rodenhouse, M. S. Webster and R. T. Holmes. (2013). Warm springs, early lay dates, and double brooding in a North American migratory songbird, the Black-throated Blue Warbler. PLoS ONE 8 (4):e59467. Close Townsend et al. 2013, Townsend, A. K., E. G. Cooch, T. S. Sillett, N. L. Rodenhouse, R. T. Holmes and M. S. Webster. (2016). The interacting effects of food, spring temperature, and global climate cycles on population dynamics of a migratory songbird. Global Change Biology 22 (2):544-555. Close Townsend et al. 2016, Lany, N. K., M. P. Ayres, E. E. Stange, T. S. Sillett, N. L. Rodenhouse and R. T. Holmes. (2016). Breeding timed to maximize reproductive success for a migratory songbird: The importance of phenological asynchrony. Oikos 125 (5):656-666. Close Lany et al. 2016).

The Black-throated Blue Warbler is one of the most intensively studied migratory passerine species in North America, and research on its populations has led to a number of conceptual advances. It is one of the few migratory songbirds for which the demography of populations has been examined in both breeding and overwintering areas. Most of these studies have focused on the factors and processes that limit and/or regulate populations and where they operate; for example, in breeding and non-breeding seasons (see reviews by Holmes, R. T. (2007). Understanding population change in migratory songbirds: Long-term and experimental studies of Neotropical migrants in breeding and wintering areas. Ibis 149 (2):2-13. Close Holmes 2007, Holmes, R. T. (2011). Avian population and community processes in forest ecosystems: Long-term research in the Hubbard Brook Experimental Forest. Forest Ecology and Management 262 (1):20-32. Close Holmes 2011; Demography: Population Regulation and Limitation). In addition, survivorship has been assessed for oversummer (May–August), overwinter (October–March), and migratory periods ( Sillett, T. S. and R. T. Holmes. (2002). Variation in survivorship of a migratory songbird throughout its annual cycle. J. Anim. Ecol. 71:296-308. Close Sillett and Holmes 2002), which is unique for any migratory passerine. Also, the connectivity between breeding and overwintering sites for individuals and populations has been examined through analyses of stable-isotope ratios in warbler tissues, mainly feathers ( Chamberlain, C. P., J. D. Blum, R. T. Holmes, X. Feng, T. W. Sherry and G. R. Graves. (1997). The use of isotope tracers for identifying populations of migratory birds. Oecologia 109 (1):132-141. Close Chamberlain et al. 1997, Rubenstein, D. R., C. P. Chamberlain, R. T. Holmes, M. P. Ayres, J. R. Waldbauer, G. R. Graves and N. C. Tuross. (2002). Linking breeding and wintering ranges of a Neotropical migrant songbird using table isotopes. Science 295:591-593. Close Rubenstein et al. 2002, Graves, G. R., C. S. Romanek and A. R. Navarro. (2002). Stable isotope signature of philopatry and dispersal in a migratory songbird. Proceedings of the National Academy of Sciences USA 99:8096-8100. Close Graves et al. 2002, Bearhop, S., G. M. Hilton, S. C. Votier and S. Waldron. (2004). Stable isotope ratios indicate that body condition in migrating passerines is influenced by winter habitat. Proc. Royal Soc. Lond. B 271:S215-S218. Close Bearhop et al. 2004) and recently with geolocators (M. T. Hallworth, unpublished data).

Many other aspects of the species’ natural history, ecology, and behavior have been studied in varying amounts of detail, including population fluctuations and regional synchrony in breeding areas ( Holmes, R. T. and T. W. Sherry. (2001). Thirty-year bird population trends in an unfragmented temperate deciduous forest: importance of habitat change. Auk 118:589-609. Close Holmes and Sherry 2001, Jones, J., P. J. Doran and R. T. Holmes. (2003b). Climate and food synchronize regional forest bird abundances. Ecology 84:3024-3032. Close Jones et al. 2003b), range-wide age-ratios ( Graves, G. R. (1997b). Geographic clines of age ratios of Black-throated Blue Warblers (Dendroica caerulescens). Ecology 78:2524-2531. Close Graves 1997b), breeding habitat use and nest-site selection ( Steele, B. B. (1992). Habitat selection by breeding Black-throated Blue Warblers (Dendroica caerulescens) at two spatial scales. Ornis Scand. 23:33-42. Close Steele 1992, Steele, B. B. (1993). Selection of foraging and nesting sites by Black-throated Blue Warblers: their relative influence on habitat choice. Condor 95:568-579. Close Steele 1993, Holmes, R. T., P. P. Marra and T. W. Sherry. (1995). Habitat-specific demography of breeding Black-throated Blue Warblers (Dendroica caerulescens): implications for population dynamics. J. Anim. Ecol. 65:183-195. Close Holmes et al. 1995, Hahn, B. A. and E. D. Silverman. (2007). Managing breeding forest songbirds with conspecific song playbacks. Animal Conservation 10 (4):436-441. Close Hahn and Silverman 2007, Betts, M. G., A. S. Hadley, N. Rodenhouse and J. J. Nocera. (2008a). Social information trumps vegetation structure in breeding-site selection by a migrant songbird. Proceedings of the Royal Society B-Biological Sciences 275 (1648):2257-2263. Close Betts et al. 2008a, Betts, M. G., N. L. Rodenhouse, T. S. Sillett, P. J. Doran and R. T. Holmes. (2008b). Dynamic occupancy models reveal within-breeding season movement up a habitat quality gradient by a migratory songbird. Ecography 31 (5):592-600. Close Betts et al. 2008b, Goetz, S. J., D. Steinberg, M. G. Betts, R. T. Holmes, P. J. Doran, R. Dubayah and M. Hofton. (2010). Lidar remote sensing variables predict breeding habitat of a Neotropical migrant bird. Ecology 91 (6):1569-1576. Close Goetz et al. 2010), foraging behavior and ecology ( Holmes, R. T., R. E. Bonney, Jr., and S. W. Pacala. (1979b). Guild structure of the Hubbard Brook bird community: a multivariate approach. Ecology 60:512-520. Close Holmes et al. 1979b, Holmes, R. T. and S. K. Robinson. (1981). Tree species preferences of foraging insectivorous birds in a northern hardwood forest. Oecologia 48:31-35. Close Holmes and Robinson 1981, Robinson, S. K. and R. T. Holmes. (1982). Foraging behavior of forest birds: the relationships among search tactics, diet, and habitat structure. Ecology 63:1918-1931. Close Robinson and Holmes 1982, Robinson, S. K. and R. T. Holmes. (1984). Effects of plant species and foliage structure on the foraging behavior of forest birds. Auk 101:672-684. Close Robinson and Holmes 1984, Holmes, R. T. (1986). Foraging patterns of forest birds: male-female differences. Wilson Bulletin 98:196-213. Close Holmes 1986, Holmes, R. T. and J. C. Schultz. (1988). Food availability for forest birds: effects of prey distribution and abundance on bird foraging. Can. J. Zool. 66:720-728. Close Holmes and Schultz 1988), mating systems and paternity ( Chuang, H. C., M. S. Webster and R. T. Holmes. (1999). Extrapair paternity and local synchrony in the Black-throated Blue Warbler. Auk 116:726-736. Close Chuang et al. 1999, Chuang-Dobbs, H. C., M. S. Webster and R. T. Holmes. (2001a). Paternity and parental care in the Black-throated Blue Warbler, Dendroica caerulescens. Anim. Behav. 62:83-92. Close Chuang-Dobbs et al. 2001a, Chuang-Dobbs, H. C., M. S. Webster and R. T. Holmes. (2001b). The effectiveness of mate guarding by male Black-throated Blue Warblers. Behavioral Ecology 12:541-546. Close Chuang-Dobbs et al. 2001b, Webster, M. S., H. C. Chuang-Dobbs and R. T. Holmes. (2001). Microsatellite identification of extrapair sires in a socially monogamous warbler. Behav. Ecol. 12:439-446. Close Webster et al. 2001, Kaiser, S. A., T. S. Sillett and M. S. Webster. (2014). Phenotypic plasticity in hormonal and behavioural responses to changes in resource conditions in a migratory songbird. Animal Behaviour 96:19-29. Close Kaiser et al. 2014, Kaiser, S. A., T. S. Sillett, B. B. Risk and M. S. Webster. (2015). Experimental food supplementation reveals habitat-dependent male reproductive investment in a migratory bird. Proceedings of the Royal Society B-Biological Sciences 282 (1803). Close Kaiser et al. 2015, Kaiser, S. A., B. B. Risk, T. S. Sillett and M. S. Webster. (2017a). Ecological and social factors constrain spatial and temporal opportunities for mating in a migratory songbird. American Naturalist 189 (3):283-296. Close Kaiser et al. 2017a, Cline, M. H., J. L. Hatt, M. J. Conroy and R. J. Cooper. (2016). Experimental evidence for a phenotypic trait as an age-dependent intrasexual social signal between familiar individuals. Animal Behaviour 111:319-327. Close Cline et al. 2016), sex-ratio bias (K. Grabenstein, MSW, unpublished data), and parental care ( Stodola, K. W., E. T. Linder, D. A. Buehler, K. E. Franzreb and R. J. Cooper. (2009). Parental care in the multi-brooded Black-throated Blue Warbler. Condor 111 (3):497-502. Close Stodola et al. 2009, Stodola, K. W., E. T. Linder, D. A. Buehler, K. E. Franzreb, D. H. Kim and R. J. Cooper. (2010). Relative influence of male and female care in determining nestling mass in a migratory songbird. Journal of Avian Biology 41 (5):515-522. Close Stodola et al. 2010, Kaiser, S. A., T. S. Sillett and M. S. Webster. (2014). Phenotypic plasticity in hormonal and behavioural responses to changes in resource conditions in a migratory songbird. Animal Behaviour 96:19-29. Close Kaiser et al. 2014). Another extensive line of research has considered how this species responds to, and is affected by, environmental change, including that brought about by forest management practices (e.g., Bourque, J. and M. A. Villard. (2001). Effects of selection cutting and landscape-scale harvesting on the reproductive success of two neotropical migrant bird species. Conservation Biology 15 (1):184-195. Close Bourque and Villard 2001, Harris, R. J. and J. M. Reed. (2001). Territorial movement of Black-throated Blue Warblers in a landscape fragmented by forestry. Auk 112:544-549. Close Harris and Reed 2001, Harris, R. J. and J. M. Reed. (2002b). Effects of forest-clearcut edges on a forest-breeding songbird. Can. J. Zool. 80:1026-1037. Close Harris and Reed 2002b, Harris, R. J. and J. M. Reed. (2002a). Behavioral barriers to non-migratory movements of birds. Ann. Zool. Fennici 39:275-290. Close Harris and Reed 2002a, Jones, J., P. J. Doran and R. T. Holmes. (2003b). Climate and food synchronize regional forest bird abundances. Ecology 84:3024-3032. Close Jones et al. 2003b, Betts, M. G., G. J. Forbes and A. W. Diamond. (2007). Thresholds in songbird occurrence in relation to landscape structure. Conservation Biology 21 (4):1046-1058. Close Betts et al. 2007, Cornell, K. L. and T. M. Donovan. (2010a). Effects of spatial habitat heterogeneity on habitat selection and annual fecundity for a migratory forest songbird. Landscape Ecology 25 (1):109-122. Close Cornell and Donovan 2010a, Cornell, K. L. and T. M. Donovan. (2010b). Scale-dependent mechanisms of habitat selection for a migratory passerine: An experimental approach. Auk 127 (4):899-908. Close Cornell and Donovan 2010b, Chandler, C. C., D. I. King and R. B. Chandler. (2012). Do mature forest birds prefer early-successional habitat during the post-fledging period? Forest Ecology and Management 264:1-9. Close Chandler et al. 2012, Hache, S., T. Petry and M.-A. Villard. (2013). Numerical response of breeding birds following experimental selection harvesting in northern hardwood forests. Avian Conservation and Ecology 8 (1). Close Hache et al. 2013), invasive species ( Stodola, K. W., E. T. Linder and R. J. Cooper. (2013). Indirect effects of an invasive exotic species on a long-distance migratory songbird. Biological Invasions 15 (9):1947-1959. Close Stodola et al. 2013), and a changing climate ( Rodenhouse, N. L. (1992). Potential effects of climatic change on migrant land birds: a simulation model. Conserv. Biol. 6:263-272. Close Rodenhouse 1992, Rodenhouse, N. L., S. N. Matthews, K. P. McFarland, J. D. Lambert, L. R. Iverson, A. Prasad, T. S. Sillett and R. T. Holmes. (2008a). Potential effects of climate change on birds of the Northeast. Mitigation and Adaptation Strategies for Global Change 13 (5-6):517-540. Close Rodenhouse et al. 2008a, Rodenhouse, N. L., L. M. Christenson, D. Parry and L. E. Green. (2009). Climate change effects on native fauna of northeastern forests. Canadian Journal of Forest Research 39 (2):249-263. Close Rodenhouse et al. 2009, Townsend, A. K., T. S. Sillett, N. K. Lany, S. A. Kaiser, N. L. Rodenhouse, M. S. Webster and R. T. Holmes. (2013). Warm springs, early lay dates, and double brooding in a North American migratory songbird, the Black-throated Blue Warbler. PLoS ONE 8 (4):e59467. Close Townsend et al. 2013, Townsend, A. K., E. G. Cooch, T. S. Sillett, N. L. Rodenhouse, R. T. Holmes and M. S. Webster. (2016). The interacting effects of food, spring temperature, and global climate cycles on population dynamics of a migratory songbird. Global Change Biology 22 (2):544-555. Close Townsend et al. 2016, Kaiser, S. A., T. S. Sillett and M. S. Webster. (2014). Phenotypic plasticity in hormonal and behavioural responses to changes in resource conditions in a migratory songbird. Animal Behaviour 96:19-29. Close Kaiser et al. 2014, Lany, N. K., M. P. Ayres, E. E. Stange, T. S. Sillett, N. L. Rodenhouse and R. T. Holmes. (2016). Breeding timed to maximize reproductive success for a migratory songbird: The importance of phenological asynchrony. Oikos 125 (5):656-666. Close Lany et al. 2016).

The extensive knowledge about the ecology and behavior of this species contributes to understanding of the factors and processes that affect the distribution and abundance of migratory passerines in general, and thus, to their conservation. However, much remains to be learned about its life history, population ecology, and responses to a changing environment.