Chestnut-sided Warbler

Distribution and Abundance

• BBS Map
• Breeding range eastern North America from southern Canada southward through Appalachian Mountains.
• Since early 1800s, major expansion in numbers and range in response to land clearing and subsequent forest regeneration. Range has expanded southward and westward with a concurrent decrease in numbers in urban and agricultural areas. Some reoccupation of previous range in the Twin City area of Minnesota in the mid-1980s (Janssen 1987). 
• Disappeared from southern portions of Wisconsin and Minnesota as land was cleared, agriculture expanded, and areas urbanized (Janssen 1987, Robbins 1990). Also disappeared from southern Illinois (Gault 1982, Bohlen 1989) and southern Missouri (Robbins and Easterla 1992).
• Localized and scarce throughout southern portions of range.  In Appalachian Mountains, restricted to higher elevations, greater than 450 m (Kain 1987, Hamel 1992).
• Rangewide, populations have undergone a slow decline from the early 1960s to the present (Droege and Sauer 1989, Sauer and Droege 1992, Whitham and Hunter 1992).
• Winters in Central America.

Habitat

• Early successional deciduous habitats. Becomes most common in deciduous second growth of large forest clearings. Both wet and dry habitats used. 
• In Wisconsin, 44% of 991observations from 1995-2000 were in upland shrub hardwood or upland mixed shrub, particularly areas formerly forested that had been heavily logged or burned, 26% in upland hardwood forest, particularly aspen or maple,  and 12.8% in upland mixed forest (WSO 2002). In southern Michigan, this species was predominately found in drier open woodlands with relatively mature trees; in northern Michigan, preferred habitats were moist or dry shrubby areas or areas of young deciduous growth (Brewer et al. 1991). 
• In north-central Minnesota, occurs in open fields with shrubs (Collins et al. 1982) yet largely absent from agricultural areas of Wisconsin (Robbins 1990) and southern Ontario (James 1991).
• Forages in scrubby patches. In second-growth forests in northern Wisconsin, males use hardwood and aspen habitats, whereas females forage in hardwood, aspen and shrub (Sodhi and Paszkowski 1995).
• Nest site in shrubby understory close to the ground. In Ontario, deciduous trees and shrubs preferred to conifers (Peck and James 1987). Nest sites have fewer and smaller trees and less canopy cover than perch sites within the territory (Collins 1981).
• During migration, occupies a wide range of forested or shrubby habitats. In Illinois, found in woodlands of all types (Bohlen 1989).
• On wintering grounds, found in equal densities in old and young forest, although prefers mature and late second growth; often found in the mid- to upper canopy of dense, moist forest (Greenberg 1984). Also inhabits coffee plantations and riparian vegetation (Stiles and Skutch 1989).

Behavior

• Predominately insectivorous, but will eat some seeds and fruit.
• Not overly agonistic; few actual encounters, mainly at territory boundaries (Ficken and Ficken 1965). Male establishes territory by continuous singing and will chase intruders. Territory size variable (from less than 0.504 to 1.10 ha), but male uses larger area during incubation (Kendeigh 1945). Interspecific territoriality with Yellow Warblers when they hold adjacent territories (Morse 1966).
• Apparently monogamous.  During breeding season in Minnesota, evidence of floater males (Rappole et al. 1977).
• On winter grounds, exhibit intraspecific territoriality (Gradwohl and Greenberg 1980), but join mixed-species feeding flocks.

Parasitism and Predation

• Brown-headed Cowbird only known brood parasite. In Ontario, approximately 21% of 211 nests studied were parasitized (Peck and James 1987) and 20% of 150 nests studied were parasitized (Friedmann et al. 1977); in Michigan, 45% of 11 nests studied were parasitized (Tate 1970).
• In Wisconsin, 13 of 477 confirmed Brown-headed Cowbird observations from 1995-2000 listed Chestnut-sided Warbler as host species (WSO 2002). 
• Cowbird eggs reported buried in nests (Friedmann 1964, Tate 1970). 
• Likely predators of eggs and nestlings include red squirrel, raccoon, opossum, weasels, striped skunk, Blue Jay, black rat snake, flying squirrels, and chipmunks.

Conservation and Management

• A study of fenitrothion-sprayed areas indicates that this species continues to forage in treated areas but returns in smaller numbers in subsequent years (Millikin and Smith 1990).
• During migration, found dead at the base of television towers, smokestacks, and buildings (Johnston and Haines 1957, Graber et al. 1983, Weir 1989).
• Unlike many bird species, Chestnut-sided Warbler responds favorably to areas cleared and allowed to regenerate. In clear-cut areas of northern Minnesota, higher densities of this species occur with increased vegetation complexity, particularly density of shrubs greater than 1 m, increased basal areas of shrubs, and increased mean height of shrubs (Niemi and Hanowski 1984). 
• Densities decline as deer browsing increases (DeGraaf et al. 1991).
• In Nova Scotia, no birds of this species occurred in uncut plots, 40-190 pairs/km² in clear-cut plots, and 50-110 pairs/km² in thinned and strip-cut plots (Freedman et al. 1981).
• BBS trend results from 1966-2000 (Sauer et al. 2001) in the Northern Spruce-Hardwoods region indicate the Chestnut-sided Warbler population has been reasonably stable in this region  (-0.4, p=0.34 Trend Graph S28); on the other hand, in the Great Lakes Transition region, this species has been increasing (1.9, p=0.06 Trend Graph S20). Survey-wide (US and Canada), this species has overall shown a slight decrease (-0.7, p=0.06 Trend Graph SUR).

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

References

• Bohlen, H.D. 1989. The birds of Illinois. Indiana Univ. Press, Indianapolis.
• Brewer, R., G.A. McPeek and R.J. Adams, Jr. 1991. The atlas of breeding birds of Michigan. Michigan State University Press, East Lansing.
• Collins, S.L. 1981. A comparison of nest-site and perch-site vegetation structure for seven species of warblers. Wilson Bull. 93:542-547.
• Collins, S.L., F.C. James and P.G. Risser. 1982. Habitat relationships of wood warblers in northern central Minnesota. Oikos 39:50-58.
• DeGraaf, R.M., W.M. Healy and R.T. Brooks. 1991. Effects of thinning and deer browsing on breeding birds in New England oak woodlands. Forest Ecology and Management 41:179-191.
• Droege, S. and J.R. Sauer. 1989. North American Breeding Bird Survey: annual summary 1988. U.S. Fish Wildl. Ser. Biol. Rep. 89(13).
• Ficken, M.S. and R.W. Ficken. 1965. Comparative ethology of the Chestnut-sided Warbler, Yellow Warbler, and American Redstart. Wilson Bull. 77:363-375.
• Freedman, B., C. Beauchamp, I.A. McLaren and S.I. Tingley. 1981. Forestry management practices and populations of breeding birds in a hardwood forest in Nova Scotia. Can. Field-Nat. 95:307-311.
• Friedmann, H., L.F. Kiff and S.J. Rothestein. 1977. A further contribution to the knowledge of the host relations of parasitic cowbirds. Smithson. Contrib. Zool. 235.
• Gault, B.T. 1982. The Chestnut-sided Warbler nesting in Missouri. Auk 9:396.
• Graber, J.W., R.R. Graber and E.L. Kirk. 1983. Illinois birds: wood warblers. Biol. Notes 118, Nat. Hist. Surv., Urbana, IL.
• Gradwohl, J. and R. Greenberg. 1980. The formation of antwren flocks on Carro Colorado Island, Panama. Auk 97:385-395.
• Greenberg, R. 1984. The winter exploitation systems of Bay-breasted and Chestnut-sided warblers in Panama. Univ. Calif. Publ. Zool. 116.
• Hamel, P.B. 1992. The land manager's guide to the birds of the south. The Nature Conservancy and U.S. Forest Service, Chapel Hill, NC.
• James, R.D. 1991. Annotated checklist of the birds of Ontario. R. Ont. Mus., Toronto.
• Janssen, R.B. 1987. Birds in Minnesota. Univ. of Minnesota Press, Minneapolis.
• Johnston, D.W. and T.P. Haines. 1957. Analysis of mass bird mortality in October, 1954. Auk 74:447-458.
• Kain, T., ed. 1987. Virginia's birdlife: an annotated checklist. 2nd ed. Virginia Avifauna no. 3.
• Kendeigh, S.C. 1945. Nesting behavior of wood-warblers. Wilson Bulletin 57:145-164.
• Millikin, R.L. and J.N.M. Smith. 1990. Sublethal effects of fenitrothion on forest passerines. J. Applied Ecol. 27:983-1000.
• Morse, D.H. 1966. The context of songs in the Yellow Warbler. Wilson Bull. 78:444-455.
• Niemi, G.J. and J.M. Hanowski. 1984. Relationships of breeding birds to habitat characteristics in logged areas. J. Wildl. Manage. 48:438-443.
• Peck, G. and R. James. 1987. Breeding birds of Ontario: nidiology and distribution. Vol. 2. Passerines. R. Ont. Mus. Life Sci. Misc. Publ., Toronto.
• Rappole, J.H., D.W. Warner and M.A. Ramos. 1977. Territoriality and population structure in a small passerine community. Am. Midl. Nat. 97:110-119.
• Robbins, M.B. and D.A. Easterla. 1992. Birds of Missouri: their distribution and abundance. Univ. of Missouri Press, Columbia.
• Robbins, S.D., Jr. 1990. Wisconsin Birdlife. Univ. of Wisconsin Press, Madison.
• Sauer, J.R. and S. Droege. 1992. Geographic patterns in population trends of neotropical migrants in North America. Pp. 26-42 in Ecology and conservation of neotropical migrant landbirds (J.M Hagen III and D.W. Johnston, eds.). Smithson. Inst. Press, Washington, D.C.
• 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.
• Sodhi, N.S. and C.A. Paszkowski. 1995. Habitat use and foraging behavior of four parulid warblers in a second-growth forest. J. Field Ornithol. 66(2):277-288.
• Stiles, F.G. and A.F. Skutch. 1989. A guide to the birds of Costa Rica. Cornell Univ. Press, Ithaca, NY.
• Tate, J. Jr., 1970. Nesting and development of the Chestnut-sided Warbler. Jack-Pine Warbler 48:57-65.
• Weir, R.D. 1989. Birds of the Kingston region. Quarry Press, Kingston, ON.
• Whitham, J.W. and M.L. Hunter, Jr. 1992. Population trends of neotrpical migrant landbirds in northern coastal New England. Pp. 85-95 in Ecology and conservation of neotropical migrant landbirds (J.M Hagen III and D.W. Johnston, eds.). Smithson. Inst. Press, Washington, D.C.
• Wisconsin Society for Ornithology. 2002. Wisconsin Breeding Bird Atlas.