Scarlet Tanager

Distribution and Abundance

• BBS Map
• Breeding range central and northern eastern United States and adjacent areas of southern Canada; range boundaries coincide with Eastern Deciduous Forest Biome (Erskine 1992, Peterjohn 1994, Price et al. 1995).
• Breeding range may have contracted eastward from Dakotas, Kansas and Oklahoma (Baumgartner 1992, Peterson 1995, Busby and Zimmerman 2001), although range may be expanding eastward in South Carolina since late 1980s (McNair and Post 1993); in Canada range may be expanding westward (Godfrey 1986, Walley 1989, Smith 1996).
• Breeding densities vary geographically, as well as among forest areas of different sizes within same geographic region (Price et al. 1995). In southern Wisconsin, density ranged from 0-2 birds on plots less than 12 ha, and 1-2.5 birds on plots greater than 50 ha; birds absent from plots less than 5 ha (Ambuel and Temple 1983). 
• BBS data from 1966-1996 indicate significant population increases in Great Lakes Plain and Great Lakes Transition areas.
• Winters in northwestern South America; although infrequently observed and range poorly known.

Habitat

• Prefers mature forest, especially where oaks are common, but may occur in young successional woodlands. Occasionally occurs in extensive plantings of shade trees in suburban areas, parks, and cemeteries (A.O.U. 1998, Isler and Isler 1999).
• In Wisconsin, of 923 observations from 1995-2000 where habitat type was reported, 66.8% were in upland hardwood forest, particularly maple or oak; 19.6% of observations were in upland mixed forest, particularly with pine (WSO 2002). In Michigan, this species showed marked preference for dry mixed oak-pine forest and dry deciduous forest, followed by mesic deciduous forest and mesic mixed forest (Brewer et al. 1991).
• In northeast United States, occurs in a wide variety of forest types ranging from pine-oak woodland, eastern hemlock-northern hardwoods, dry oak-hickory woodland, beech forests, and occasionally pure stands of eastern hemlock (Laughlin and Kibbe 1985, Brauning 1992, Bevier 1994)
• Shows a marked dependency on size of forest tract; estimated minimum forest area needed to sustain a viable population is 10-12 hectares (Galli et al. 1976, Robbins 1980, Robbins et al. 1989, Roberts and Norment 1999). Across its entire breeding range, occurrence significantly affected by proportion of landscape in forest cover. In northern forest regions of upper midwest east to Nova Scotia, where more than 70% forested, Scarlet Tanagers found in comparable densities in forest patches of all sizes but as forest cover drops to 40%, tanagers found in same densities as unfragmented forest only when patches 90 acres or more (see table in Rosenberg et al. 1999).
• Nesting birds prefer deciduous trees of considerable height  and size (Prescott 1965, Anderson and Shugart 1974); a Michigan study indicated a high probability of occurrence of this species in forested areas with a moderate density of large trees and a low density of small trees (Porter 1996).
• Forages in both trees and shrubs (Prescott 1965, Maurer and Whitmore 1981, Sabo and Holmes 1983). In trees, primarily forages in midcanopy; dominant tree species are yellow birch, American beech, and sugar maple (Holmes and Robinson 1981, Holmes 1986).
• Migratory habitat includes a variety of wooded habitats with tall trees, similar to those used in breeding; also occurs in more open habitats such as woodlands, parks, and gardens (Isler and Isler 1999).
• Winter habitat appears to be primarily midcanopy of montane evergreen forests and forests of steep-sloped, well-drained foothills.

Behavior

• Diet during breeding season mostly insectivorous; when insects not plentiful, will take earthworms as well as variety of wild and cultivated fruits. During migration and in winter range, regularly takes fruit as well as insects. 
• Aggressive encounters between conspecifics most common shortly after arrival of males on breeding grounds during establishment of territories. Territory sizes range from 0.9-1.2 ha in Quebec (Gauthier and Aubry 1996), 0.8-2.4 ha in Maryland (Robbins 1980), 2.5-5.0 ha in New Hampshire (Zumeta and Holmes 1978), 6.13-7.6 ha in New York (Roberts and Norment 1999), 3.75-12.5 ha in Illinois (Robinson 1992), 2.5 ha in Wisconsin (Emlen 1984).
• Males also observed to direct aggression towards females attempting to leave territory. Once paired, females may chase other females from territory.
• Presumed seasonally monogamous; pairs forage together during breeding season.
• Countersings to songs of Summer Tanager along adjacent territorial boundaries; interspecific aggression suspected when boundaries disputed (Shy 1984). Occasionally aggressive toward other species when they approach too near the nest. Observed chasing more than 15 different species of birds; aggression toward Blue Jay particularly  pronounced, often involving physical contact (Prescott 1965).
• Migrates singly or in small loose flocks with other neotropical migrants (e.g., warblers, thrushes, vireos).
• In winter range, tends to be solitary, but joins mixed-species flocks for foraging.

Parasitism and Predation

• Parasitized by Brown-headed Cowbird throughout its range (Friedmann 1963). Variability in parasitism due in part to geography; there are more cowbirds in the midwest than in the north or northeast (Rosenberg et al. 1999). Lower rates of parasitism in landscapes that are less fragmented and contain larger forested tracts. The highly fragmented landscape of Illinois, where greater than 80% of nests are parasitized is considered to represent a population sink  (Robinson et al. 1995, Brawn and Robinson 1996, Bollinger et al. 1997).
• In Wisconsin, 17 of 477 confirmed Brown-headed Cowbird observations from 1995-2000 listed Scarlet Tanager as host species (WSO 2002).
• When male and female tanagers detect a female cowbird approaching the nest area, they aggressively drive her from their territory; once the female cowbird slips her egg in the nest undetected, apparently tanagers are unable to differentiate cowbird eggs/young from their own (Prescott 1965).
• Adults observed as prey of Eastern Screech Owl, Long-eared Owl, Short-eared Owl, and Merlin. Nest predators include Blue Jay, Grackles, and American Crow. Squirrels, chipmunks and snakes also likely nest predators, but no observations of nest disturbance by these groups (Prescott 1965).

Conservation and Management

• Disturbances in forest canopy during breeding season adversely affected Scarlet Tanagers in central Michigan (Porter 1996). Study sites that had tanagers during the first census, but were then selectively logged, did not appear to have tanagers on subsequent censuses or the following year.
• Prevention of further habitat loss and preservation and restoration of extensive forested areas on breeding grounds should be primary management strategy (Robbins et al. 1989, Robinson et al. 1995, Villard et al. 1999).
• Reduced reproductive success in fragmented forests appears to result from high rates of nest predation and brood parasitism by cowbirds. Since nest predation and parasitism rates appear to be inversely related to size of forest fragment, emphasis should be on preserving largest possible forest tracts within each region of the breeding range of this species (Robinson et al. 1995). Selective logging, and other forest canopy disturbances should be limited to nonbreeding season (Porter 1996).
• BBS trend results from 1966-2000 (Sauer et al. 2001) in the Northern Spruce-Hardwoods region indicate the Scarlet Tanager has overall remained reasonably stable  (-0.8, p=0.12 Trend Graph S28), although in the period from 1980-2000, this species has been declining (-1.8, p-0.03); on the other hand, in the Great Lakes Transition region, this species has been increasing (1.9, p=0.02 Trend Graph S20). Survey-wide (US and Canada), this species has overall experienced no change in population (-0.2, p=0.37 Trend Graph SUR).

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

References

• Ambuel, B. and S.A. Temple. 1983. Area-dependent changes in the bird communities and vegetation of southern Wisconsin forests. Ecology 64:1057-1068.
• American Ornithologist's Union. 1998. Checklist of North American Birds. 7th edition. Washington, D.C.
• Anderson, S.H. and H.H. Shugart. 1974. Habitat selection of breeding birds in an east Tennessee deciduous forest. Ecology 55:828-837.
• Baumgartner, F.M. and A.M. Baumgartner. 1992. Oklahoma bird life. University of Oklahoma Press, Norman, OK.
• Bevier, L.R., ed. 1994. The atlas of breeding birds of Connecticut. State Geol. Nat. Hist. Surv. Connecticut Bull. no. 113.
• Bollinger, E.K., B.D. Peer and R.W. Jansen. 1997. Status of Neotropical migrants in three forest fragments in Illinois. Wilson Bulletin 109:521-526.
• Brauning, D.W., ed. 1992. Atlas of breeding birds of Pennsylvania. University of Pittsburgh Press, Pittsburgh, PA.
• Brawn, J.D. and S.K. Robinson. 1996. Source-sink population dynamics may complicate the interpretation of long-term census data. Ecology 77:3-12.
• Brewer, R., G.A. McPeek and R.J. Adams, Jr. 1991. The atlas of breeding birds of Michigan. Michigan State University Press, East Lansing, MI.
• Busby, W.H. and J.L. Zimmerman. 2001. Kansas Breeding Bird Atlas. University Press of Kansas.
• Emlen, J.T. 1984. An observer-specific, full-season, strip-map method for censusing song bird communities. Auk 101:730-740.
• Erskine, A.J. 1992. Atlas of breeding birds of the Maritime Provinces. Nimbus Publ. and Nova Scotia Mus., Halifax.
• Friedmann, H. 1963. Host relations of the parasitic cowbirds. Smithsonian Inst. Mus. of Nat. Hist., Washington, D.C.
• Galli, A.E., C.F. Leck and R.T.T. Forman. 1976. Avian distribution patterns in forest islands of different sizes in central New Jersey.
• Gautheir, J. and Y. Aubry, eds. 1996. The breeding birds of Quebec: atlas of the breeding birds of Southern quebec. Province of Quebec Society for the Protection of Birds, Can. Wildl. Serv., Environ. Canada.
• Godfrey, W.E. 1986. The birds of Canada. Natl. Mus. Canada, Ottawa, ON.
• 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. 1986. Foraging patterns of forest birds: male-female differences. Wilson Bulletin 98:196-213.
• Isler, M.L. and P.R. Isler. 1999. The Tanagers: natural history, distribution, and identification. Smithsonian Inst. Press, Washington, D.C.
• Laughlin, S.B. and D.P. Kibbe, eds. 1985.  The atlas of breeding birds in Vermont. University Press of New England, Hanover, NH.
• Maurer, B.A. and R.C. Whitmore. 1981. Foraging of five bird species in two forests with different vegetation structure. Wilson Bulletin 93:478-490.
• McNair, D.B. and W. Post. 1993. Supplement to status and distribution of South Carolina birds. Charleston Mus. Ornithol. Contrib. no. 8.
• Peterjohn, B.G. 1994. The North American breeding bird survey. Birding 26:387-398.
• Peterson, R.A. 1995. The South Dakota breeding bird atlas. South Dakota Ornithol. Union. Aberdeen, SD.
• Price, J., S. Droege and A. Price. 1995. Summer atlas of North American Birds. Academic Press, London, England.
• Porter, T.W. 1996. Habitat selection by the Scarlet Tanager in the Manistee National Forest. M.S. Thesis, Central Michigan University, Mt. Pleasant, MI.
• Prescott, K.W. 1965. The Scarlet Tanager. NJ State Mus. Invest. no. 2.
• Price, J., S. Droege and A. Price. 1995. Summer atlas of North American birds. Academic Press, London, England.
• Robbins, C.S. 1980. Effect of forest fragmentation on breeding bird populations in the piedmont of the mid-Atlantic region. Atlantic Nat. 33:31-36.
• Robbins, C.S., D.K. Dawson and B.A. Dowell. 1989. Habitat area requirements of breeding forest birds of the Middle Atlantic states. Wildl. Monogr. 103.
• Roberts, C. and C.J. Norment. 1999. Effects of plot size and habitat characteristics on breeding success of Scarlet Tanagers. Auk 116:73-82.
• Robinson, S.K. 1992. Population dynamics of Neotropical migrants in a fragmented Illinois landscape. Pp. 408-418 in Ecology and conservation of Neotropical migrant landbirds (J.M. Hagan III and D.W. Johnson, eds.). Smithsonian Inst. Press, Washington, D.C.
• Robinson, S.K., F.R. Thompson III, T.M. Donovan, D.R. Whitehead and J. Faaborg. 1995. Regional forest fragmentation and the nesting success of migratory birds. Science 267:1987-1990.
• Rosenberg, K.V., J.D. Lowe and A.A. Dhondt. 1999. Effects of forest fragmentation on breeding tanagers: a continental perspective. Conservation Biology 13:568-583.
• Sabo, S.R. and R.T. Holmes. 1983. Foraging niches and the structure of forest bird communities in contrasting montane habitats. Condor 85:121-138.
• 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.
• Shy, E. 1984. Sympatry and allopatry of song in North American tanagers. Behav. Ecol. Sociobiol. 15:189-195.
• Smith, A.R. 1996. Atlas of Saskatchewan birds. Saskatchewan Nat. Hist. Soc., Regina.
• Villard, M.A., M.K, Trzcinski and G. Merriam. 1999. Fragmentation effects on forest birds: relative influence of woodland cover and configuration on landscape occupancy. Conserv. Biol. 13:774-783.
• Walley, W.J. 1989. Breeding of the Scarlet Tanager in Western Manitoba. Can. Field-Nat. 103:572-576.
• Wisconsin Society for Ornithology. 2002. Wisconsin Breeding Bird Atlas.
• Zumeta, D.C. and R.T. Holmes. 1978. Habitat shift and roadside mortality of Scarlet Tanagers during a cold wet New England spring. Wilson Bulletin 90:575-586.