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Limnothlypis swainsonii (Audubon, 1834)
Swainson's Warbler
Federal Protection: No US federal protection
State Protection: No Georgia state protection
Global Rank: G4
State Rank: S3
Element Locations Tracked in Biotics: Yes
SWAP 2015 Species of Greatest Conservation Need (SGCN): Yes
SWAP 2025 Species of Greatest Conservation Need (SGCN): Yes
2025 SGCN Priority Tier: Moderate Conservation Concern
Element Occurrences (EOs) in Georgia: 25
Habitat Summary for element in Georgia: Dense undergrowth or canebrakes in swamps and river floodplains, small mountain pop. in rhododendron and mountain laurel thickets
The Swainson’s warbler is a drab wood warbler. Upperparts are brown to olive-brown. The underparts are a drab white or cream color. A white supercilium (eyebrow-line) and a relatively long pointed bill are the most distinctive physical features of this species. Swainson’s warbler is better known by its loud song which rings through bottomlands in the spring. This bird is generally found in brushy understory or on the ground.
Most similar in appearance to worm-eating warbler (Helmitheros vermivorum). The worm-eating warbler has broad, dark, sharply contrasting crown stripes and a dark eye-line whereas the Swainson’s warbler has a rusty cap, brown eye-line, and white supercilium. Swainson’s warbler also has a much longer bill. Both species skulk in shrubby habitats, particularly in the Blue Ridge Mountains where there is some possibility of both species occurring in the same location. In the Blue Ridge worm-eating warblers are usually found in dry oak and pine upland habitats while Swainson’s warblers are more likely to be found in wetter sites such as rhododendron slicks (thickets) with a broken canopy. The main song of the Louisiana waterthrush (Parkesia motacilla) and the Swainson’s warbler can sound very similar with the Swainson’s song most often having a clear “whip-poor-will” ending while the waterthrush usually has a more muddled ending. Waterthrushes often occur along the edges of creeks in bottomland habitats occupied by Swainson’s warblers.
The Swainson’s Warbler is unusual in being a habitat specialist, yet occupying two seemingly different habitat types, canebrakes and other thickets in the Coastal Plain and Piedmont and rhododendron slicks in the mountains. Though occasionally found in other habitats, most Swainson’s warblers in Georgia occur in vast floodplains of large rivers.
This species forages by walking on the ground under thick vegetation picking through dead leaves and other detritus for invertebrates, particularly spiders, beetles, crickets, and ants. Feeding areas are larger patches of leaf litter with little herbaceous cover.
This warbler is a habitat specialist requiring large trees with a broken canopy and dense understory thickets of cane, rhododendron, mountain laurel, palmetto, privet or vine tangles (e.g., supplejack, greenbrier). Much of its habitat in the state occurs in bottomlands along the larger rivers of the Coastal Plain and Piedmont. Although young pines can provide habitat for the Swainson’s warbler at times, this habitat type is short lived and may be of lower quality than others. Studies suggest this species may prefer wide unbroken tracts of bottomland forest over narrow floodplain forest or fragmented landscapes. In Georgia, the breeding season begins in late March or early April. The female constructs the nest, which has a loose outer layer of dried leaves, vines, sticks, and tendrils giving it the appearance of a cluster of leaves or clump of debris. The inner cup is more tightly woven and is made from skeletonized leaves and sometimes covered by twigs or pine needles. Finer materials including red maple leaf stems, Spanish moss, cypress needles or twigs, pine needles, hair, rootlets, or grass are used for lining. Usually three or four eggs (range 2-5) are laid and incubated by the female for 13-15 days before hatching. Both parents feed the young in the nest for 10-12 days before they fledge.
Point counts conducted during the breeding season in likely habitats. The use of playback may enhance the detection probability of this species.
The breeding range of the Swainson’s warbler includes much of the Southeast from south coastal Virginia westward to east Texas and Oklahoma. In Georgia, it is fairly common in appropriate habitat in the Coastal Plain, uncommon in the Piedmont, and rare in the southern Blue Ridge. However, its habitat is uncommon across the landscape.
During the Breeding Bird Atlas (1994-2001) this species was found throughout parts of the Coastal Plain, particularly along large river courses. It was much less common in the Piedmont where most records came from monitoring efforts on wildlife management areas. Only four sightings occurred in the Ridge and Valley and five sightings in the Blue Ridge. The lack of records along some of the large rivers in parts of the Lower Coastal Plain may be due to limited habitat, or more likely limited access and survey effort in these areas.
The Swainson’s warbler winters in the Caribbean in the Bahama Islands, Cuba, Isla de la Juventud (Isle of Pines), Jamaica, and the Cayman Islands and in the Yucatán Peninsula in Mexico, northern Guatemala, and Belize.
Swainson’s warbler populations appear to be stable or increasing in Georgia. At a local level, populations may be impacted by conversion of habitats to other uses and forest fragmentation. At a regional level changes in hydrology and water quality, particularly the frequency and duration of flooding could threaten this species, but no research has been conducted to investigate this relationship. Other threats to this species include reduction of understory vegetation from deer over-browsing and invasion of bottomlands by exotic plant species, especially Japanese-grass (Microstegium vimineum) and Chinese privet (Ligustrum sinense).
| Threat 1 | Threat 2 | Threat 3 | |
|---|---|---|---|
| General Threat | Natural system modifications | Agriculture & aquaculture | None |
| Specific Threat | Fire & fire suppression | Livestock farming & ranching | None |
Breeding Bird Survey (BBS) data for 1966-2015 show an annual increase of 1.2% for this species survey-wide. No reliable trend information was available for this species in Georgia during this period due to small sample size. Caution should be used when interpreting trends for this warbler since it is difficult to accurately track due to its scattered and local distribution, low densities on most BBS routes, and the fact that roadside counts generally do not adequately sample its habitats. However, anecdotal information suggests that the Swainson’s warbler may be experiencing population increases in portions of its range, including the Coastal Plain of Georgia, but at the same time may be declining in the state in the southern Blue Ridge and Piedmont.
Maintenance and restoration of healthy floodplain forests, particularly extensive canebrakes may be important for this species in the Coastal Plain. Minimizing forest fragmentation and maintaining canopy gap dynamics associated with older age classes of timber may also be important throughout this species’ range.
Beaton, G., P. W. Sykes, Jr. and J. W. Parrish, Jr. 2003. Annotated Checklist of Georgia Birds. 5th edition. Georgia Ornithological Society Occasional Publication No. 14.
Brown, R. E., and J. G. Dickson. 1994. Swainson’s Warbler (Limnothlypis swainsonii). In A. Poole and F. Gill, eds., The Birds of North America, No. 126. The Academy of Natural Sciences, Philadelphia, PA and The American Ornithologists’ Union, Washington, DC.
Burleigh, T. D. 1923. In the haunts of Swainson’s Warbler. Murrelet 4:5-7.
Burleigh, T. D. 1958. Georgia Birds. University of Oklahoma Press, Norman.
Carrie, N. R. 1996. Swainson’s Warblers nesting in early seral pine forests in East Texas. Wilson Bulletin 108:802-804.
Cleckley, M. T. 1903. Nest and eggs of the Swainson’s Warbler (Helinaia swainsonii). Auk 20:438-439.
Eddleman, W. R., K. E. Evans, and W. H. Elder. 1980. Habitat characteristics and management of Swainson’s Warbler in southern Illinois. Wildlife Society Bulletin 8:228-233.
Kilgo J. C., R. A. Sargent, B. R. Chapman, and K. V. Miller. 1998. Effect of stand width and adjacent habitat on breeding bird communities in bottomland hardwoods. Journal of Wildlife Management 62:72-83.
Klaus, N. A. 2010. Swainson’s Warbler (Limnothlypis swainsonii) Pp.352-353 in T. M. Schneider, G. Beaton, T. S. Keyes, and N. A. Klaus, eds. The Breeding Bird Atlas of Georgia. University of Georgia Press, Athens.
Meanley, B. 1945. Notes on Swainson’s Warbler in central Georgia. Auk 62:395-401.
Meanley, B. 1966. Some observations on habitats of the Swainson’s Warbler. Living Bird 5:151-165.
Meanley, B. 1969. Pre-nesting and nesting behavior of the Swainson’s Warbler. Wilson Bulletin 81:246-257.
Meanley, B. 1971a. Natural History of the Swainson’s Warbler. North American Fauna No. 69. U. S. Department of the Interior, Fish and Wildlife Service, Bureau of Sport Fisheries and Wildlife, Washington, DC.
Meanley, B. 1971b. Additional notes on pre-nesting and nesting behavior of the Swainson’s Warbler. Wilson Bulletin 83:194.
Norris, R. A., and M. Hopkins, Jr. 1947. The breeding of Swainson’s Warbler near Tifton, Georgia. Oriole 12:7-9.
Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski, Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link. 2017. The North American Breeding Bird Survey, Results and Analysis 1966-2015. Version 2.07.2017 U.S.G.S. Patuxent Wildlife Research Center, Laurel, MD.
Soule, J. 1992. Species Management Abstract: Swainson’s Warbler. The Nature Conservancy, Arlington, VA.
Wright, E. A., and J. M. Meyers. 2002. Habitat and Density of a Swainson’s Warbler Breeding Population, Bond Swamp National Wildlife Refuge. Annual Report. U. S. Fish and Wildlife Service, Atlanta, GA.
Nathan A. Klaus and Todd M. Schneider
30 October 2019
