Blackburnian Warbler

Distribution and Abundance

• BBS Map
• Breeding range northeast North America; also extending southward along Appalachian Mountains at high elevations.
• Recent range extension possible in western Canada (Bent 1953). Distribution in New York has changed over past 100 years, from concentration in mountains to expansion, especially along Appalachian Plateau (Eaton 1914, Levine 1988). Population probably increased over this time in Vermont also (Ellison 1985).
• Winters primarily in southern Central America and northern South America. 

Habitat

• Characteristically associated with coniferous and mixed coniferous-deciduous forests (A.O.U. 1983), especially mature forest (Collins et al. 1982). At southern end of range, inhabits largely or completely deciduous forest (Brooks 1940); elsewhere in range may inhabit primarily deciduous forests at low densities (Holmes et al. 1986).
• In Wisconsin, 59% of observations from 1995-2000 were in upland mixed forest; 27% of observations were in upland hardwood forest, particularly maple, or upland conifer forest, particularly pine (WSO 2002). In Michigan, this species tends to prefer mature mesic conifer forest (Brewer et al. 1991). 
• In New York state and other areas with deep coniferous forests and swamp woods at higher elevations, often prefers spruce draped with Usnea lichen (Levine 1988). Along the Maine coast, inhabits red and white spruce forests, but not on small islands less than 1 ha which generally have insufficient tall vegetation (Morse 1971, 1977). In Minnesota, found on islands of less than 1 ha only if tall pines or black spruces are available (Howe 1979, Rusterholz and Howe 1979). In eastern Canada, most common in fir-spruce and hemlock forests (Erskine 1980, 1984).
• In spruce forests, males forage in treetops at singing levels, females at height of nests (Morse 1968). At end of breeding season, shifts from spruce vegetation to paper birches when the latter contain large numbers of insects (Morse 1970).
• Nest almost without exception placed in conifers. In primarily deciduous forest in New Hampshire, nests only where conifers are available (Holmes and Robinson 1981). Prefers hemlocks in Ontario (Peck and James 1987) and in Maine, except on the coast where spruce is preferred (Morse 1968). 
• During migration, this species regularly uses all woody habitats, including forest edge (Keast 1980b, Graber et al. 1983). 
• On wintering grounds, found usually in highland or montane regions (Chipley 1980, Keast 1980a, Ridgely and Gwynne 1989).

Behavior

• Insectivorous during breeding season. Primarily insectivorous during winter, but eats some fruit (Hilty 1980, Rappole et al. 1983).
• Territorial during breeding season. Males exhibit elaborate patterns of chasing and fleeing, especially early in the season. No clear evidence for interspecific territoriality, although occasional interspecific attacks (Morse 1976b).
• Territory size varies with habitat: smaller where favored conifers are dense than in mixed coniferous-deciduous forests. Along Maine coast, territories range between 0.4-0.6 ha in both red and white spruce (Morse 1976a, 1977). Territories averaged 1.1 ha in a largely deciduous forest with occasional, patchily distributed conifers (Sherry and Holmes 1985). Territories in fir-spruce forest in Ontario ranged from 0.8-0.9 ha (Kendeigh 1947).
• Monogamous, but quiet second males sometimes seen on territories.
• Adults mob and scold predators about nest and incubating female exhibits distraction display.
• Often joins mixed-species flocks during migration (Morse 1970, Ridgely and Gwynne 1989).
• Generally solitary on wintering grounds (Skutch in Bent 1953, Slud 1964).

Parasitism and Predation

• Considered a very uncommon host for Brown-headed Cowbird (Friedmann 1963, Friedmann et al. 1977). Adults mob female cowbirds on breeding grounds, but do accept cowbird eggs and nestlings.
• In Wisconsin, only 1 of 477 confirmed Brown-headed Cowbird observations from 1995-2000 listed Blackburnian Warbler as host species (WSO 2002). Of 86 nests observed in Ontario, 9 were parasitized (Peck and James 1987).
• Population densities have not declined in extensive forested area along Maine coast over period when cowbird parasitism has been advanced as major cause of decline in other neotropical migrants (Morse 1976a).
• Predators of eggs and young primarily red squirrels and Blue Jays. Possible predators of adults include Sharp-shinned Hawks and Cooper's Hawks (Morse 1993). Nesting female taken by a Merlin (Lawrence 1953).

Conservation and Management

• Mortality associated with DDT application for Dutch Elm disease control reported (Wallace et al. 1961). Also decrease and probable mortality associated with application of fenitrothian in spruce budworm control reported (Pearce et al. 1979).
• Removal of large conifers decreases populations of this species (Webb et al. 1983). Current 50 year cutting rotations in upper peninsula of Michigan will decrease breeding habitats (Doepker et al. 1992).
• Has a "positive old-growth affinity" (it occurred in all 11 old growth hemlock-white pine-hardwood forest stands) in the northern Appalachian plateau of Pennsylvania; it had the highest territorial density of any species with a positive old-growth affinity (24 territories/10 ha). It was much less common in managed forest types in this area (Haney 1999).
• BBS trend results from 1966-2000 (Sauer et al. 2001) in the Northern Spruce-Hardwoods region indicate the Blackburnian Warbler population has increased slightly in this region  (1.4, p=0.07 Trend Graph S28); on the other hand, in the Great Lakes Transition region, this species has experienced a significant decrease (-5.3, p=0.09 Trend Graph S20). Survey-wide (US and Canada), this species has overall increased slightly (1.1, p=0.07 Trend Graph SUR).

For more information about the conservation and management of the Blackburnian Warbler, please see the Species Management Abstract, from the Conserve Online public library, maintained by The Nature Conservancy.

References

• American Ornithologists' Union. 1983. Checklist of North American Birds, 6th ed. Am. Ornithol. Union, Baltimore, MD.
• Bent, A.C. 1953. Life histories of North American wood warblers. U.S. Natl. Mus. Bull. 203.
• Brewer, R., G.A. McPeek and R.J. Adams, Jr. 1991. The atlas of breeding birds of Michigan. Michigan State University Press, East Lansing.
• Brooks, M. 1940. The breeding warblers of the central Allegheny Mountain region. Wilson Bull. 52:249-266.
• Chipley, R.M. 1980. Nonbreeding ecology of the Blackburnian Warbler. Pp. 309-317 in Migrant birds in the Neotropics (A. Keast and E.S. Morton, eds.). Smithson. Inst. Press, Washington, D.C.
• Collins, S.L., F.C. James and P.G. Risser. 1982. Habitat relationships of wood warblers in northern central Minnesota. Oikos 39:50-58.
• Doepker, R.B., R.D. Earle and J.J. Ozoga. 1992. Characteristics of Blackburnian Warbler breeding habitat in upper Michigan. Can. Field-Nat. 106:366-371.
• Eaton, E.H. 1914. Birds of New York. NY State Ed. Dept., Albany, NY.
• Ellison, W.G. 1985. Blackburnian Warbler. Pp. 298-299 in The atlas of breeding birds of Vermont (S.B. Laughlin and D.P. Kibbe, eds.). Univ. Press New England, Hanover, NH.
• Erskine, A.J. 1980. A preliminary catalogue of bird census plot studies in Canada, Pt. 4. Can. Wildl. Serv. Prog. Notes No. 112.
• Erskine, A.J. 1984. A preliminary catalogue of bird census plot studies in Canada, Pt. 4. Can. Wildl. Serv. Prog. Notes No. 144.
• Friedmann, H. 1963. Host relations of the parasitic cowbirds. U.S. Natl. Mus. Bull. 233.
• Friedmann, H., L.F. Kiff and S.I. Rothstein. 1977. A further contribution to knowledge of the host relations of parasitic cowbirds. Smithson. Contrib. Zool. 235.
• Graber, J.W., R.R. Graber and E.L. Kirk. 1983. Illinois birds: wood warblers. Biological Notes No. 118. III. Nat. Hist. Surv., Urbana, IL.
• Haney, J.C. 1999. Hierarchial comparisons of breeding birds in old-growth conifer-hardwood forest on the Appalachian Plateau. Wilson Bulletin 111:89-99.
• Hilty, S.L. 1980. Relative abundance of North Temperate Zone breeding migrants in Western Colombia and their impact at fruiting trees. Pp. 265-271 in Migrant birds in the Neotropics (A. Keast and E.S. Morton, eds.). Smithson. Inst. Press, Washington, D.C.
• Holmes, R.T. and S.K. Robinson. 1981. Tree species preferences of foraging insectivorous birds in a northern hardwoods forest. Oecologia 48:31-35.
• Holmes, R.T., T.W. Sherry and F.W. Sturges. 1986. Bird community dynamics in a temperate deciduous forest: long-term trends at Hubbard Brook. Ecol. Monogr. 56:201-220.
• Howe, R.W. 1979. Distribution and behavior of birds on small islands in northern Minnesota. J. Biogeog. 6:379-390.
• Keast, A. 1980a. Spatial relationships between migratory parulid warblers and their ecological counterparts in the Neotropics. Pp. 109-130 in Migrant birds in the Neotropics (A. Keast and E.S. Morton, eds.). Smithson. Inst. Press, Washington, D.C.
• Keast, A. 1980b. Migratory Parulidae: what can species co-occurrence in the North reveal about ecological plasticity and wintering patterns? Pp. 457-476 in Migrant birds in the Neotropics (A. Keast and E.S. Morton, eds.). Smithson. Inst. Press, Washington, D.C.
• Kendeigh, S.C. 1947. Bird population studies in the coniferous forest biome during a spruce budworm outbreak. Dept. Lands Forests, Ontario, Canada, Biol. Bull. 1:1-100.
• Lawrence, L. deK. 1953. Notes on the nesting behavior of the Blackburnian Warbler. wilson Bull. 65:135-144.
• Levine, E. 1988. Blackburnian Warbler. Pp. 382-383 in The atlas of breeding birds in New York State. Cornell Univ. Press, Ithaca, NY.
• Morse, D.H. 1968. A quantitative study of foraging of male and female spruce woods warblers. Ecology 49:779-784.
• Morse, D.H. 1970. Ecological aspects of some mixed-species foraging flocks of birds. Ecol. Monogr. 40:119-168.
• Morse, D.H. 1971. The foraging of warblers isolated on small islands. Ecology 52:216-228.
• Morse, D.H. 1976a. Variables determining the density and territory site of breeding spruce-woods warblers. Ecology 57:290-301.
• Morse, D.H. 1976b. Hostile encounters among spruce-woods warblers. Anim. Behav. 24:764-771.
• Morse, D.H. 1977. The occupation of small islands by passerine birds. Condor 79:399-412.
• Morse, D.H. 1993. Black-throated Green Warbler. In the Birds of North America, No. 55 (A. Poole and F. Gill, eds.). Acad. Nat. Sci. and Am. Ornithol. Union, Philadelphia, PA.
• Pearce, P.A., D.E. Peakall and A.J. Erskine. 1979. Impact on forest birds of the 1976 spruce budworm spray operation in New Brunswick. Can. Wildl. Serv. Prog. Notes No. 97.
• Peck, G.K. and R.D. James. 1987. Breeding birds of Ontario: nidiology and distribution. Royal Ontario Museum, Toronto, ON.
• Rappole, J.H., E.S. Morton, T.E. Lovejoy and J.L. Ruos. 1983. Nearctic avian migrants in the Neotropics. U.S. Fish Wildl. Serv. Unpubl. Rep.
• Ridgely, R.S. and J.A. Gwynne. 1989. A guide to the birds of Panama, 2nd ed. Princeton Univ. Press, Princeton, NJ.
• Rusterholz, K.A. and R.W. Howe. 1979. Species-area relations of birds on small islands in a Minnesota Lake. Evolution 33:468-477.
• Sauer, J.R., J.E. Hines and J. Fallon. 2001. The North American Breeding Bird Survey, Results and Analysis 1966-2000. Version 2001.2, USGS Patuxent Wildlife Research Center, Laurel, MD.
• Sherry, T.W. and R.T. Holmes. 1985. Dispersion patterns and habitat responses of birds in northern hardwood forests. Pp. 283-309 in Habitat selection in birds (M.L. Cody, ed.). Academic Press, New York.
• Slud, P. 1964. The birds of Costa Rica. Bull. Mus. Nat. Hist. 128:1-430.
• Wallace, G.J., W.P. Nickell and R.F. Bernard. 1961. Bird mortality in the Dutch elm disease program in Michigan. Bull. Cranbrook Inst. Sci. 41:11-44.
• Webb, W.L., D.F. Behrend and B. Saisorn. 1983. Effect of logging on songbird populations in a northern hardwood forest. Wildl. Monogr. 55:1-35.
• Wisconsin Society for Ornithology. 2002. Wisconsin Breeding Bird Atlas.