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Swamp Sparrow Life History



Swamp Sparrows nest only in wetlands. In the northern parts of the range, they use fens and bogs that have patches of open water, especially those dotted with shrubs. They also nest in peat bogs with little open water. Through most of the breeding range, look for them in freshwater marshes with cattail, sedges, and other tall reeds, rushes, or grasses; these areas often have willows or alders around their edges. In the mid-Atlantic states, “Coastal Plain” Swamp Sparrows (the nigrescens subspecies) nest in brackish marshes in tidal rivers, mostly in the higher portion of the marshes where salt-meadow hay is dotted with small shrubs like marsh elder and groundsel. During migration, large numbers of Swamp Sparrows mix with Song, Lincoln’s, and White-throated Sparrows in the East, especially in coastal locations prone to “fallouts” of migrants. In such cases, the birds might be a considerable distance from the nearest wetland.

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Like other sparrows, Swamp Sparrows feed on seeds, fruits, and invertebrates. They eat up to 85% plant matter in winter, whereas the same percentage is animal matter during spring and early summer. Known foods include ants, bees, wasps, beetles, aphids, caterpillars, grasshoppers, and crickets, as well as aquatic invertebrates such as molting damselflies and dragonflies. They also consume blueberries and the seeds of many sedges, grasses (foxtail, panic grass), swamp dock, smartweed, and vervain. Swamp Sparrows feed on seeds both on the ground and when perched in vegetation, and they readily walk onto muddy margins and wade into shallow water, even immersing the head, to capture invertebrates, which are sometimes discovered by flipping immersed vegetation. They also glean insects from shrubs during the warmer months.

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Nest Placement


The female generally selects the site for the nest, in a patch of vegetation such as grass or reeds, less often in shrubs. Nests are usually less than 3 feet off the ground and sometimes on the ground itself.

Nest Description

The female constructs the nest; the male might contribute some of the nest material but does not help her build. The nest is often hidden by overhanging vegetation. The cup’s interior is finely woven with grasses, sedges, hair, rootlets, plant fibers, and plant down; the exterior is coarser, composed of much the same material, as well as cattails, twigs, fern fronds, and leaves. Nests average 3 inches tall by 4.25 inches across, with the cup itself 2.25 inches across and 1.6 inches deep.

Nesting Facts

Clutch Size:1-6 eggs
Number of Broods:1-2 broods
Egg Length:0.6-0.8 in (1.4-2.1 cm)
Egg Width:0.6-0.6 in (1.4-1.5 cm)
Incubation Period:12-14 days
Nestling Period:7-14 days
Egg Description:

Bluish green with spots and blotches.

Condition at Hatching:

Helpless with sparse dark brown down.

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Ground Forager

Males prefer an elevated song perch in a tall shrub or sapling in their territory and may sing from well before dawn through mid-morning; some individuals also sing at night. As territories are established early in the spring, fights between rival males are not uncommon. They may also be territorial toward Song Sparrows, Marsh Wrens, and Common Yellowthroats. Swamp Sparrows are beautifully adapted to their wetland habitat, navigating agilely through dense cover whether in flight, running on the ground, or climbing through the reeds. Foraging birds walk along the water’s edge or just inside emergent vegetation, picking seeds and insects from the mud or water. In areas of leaf litter, Swamp Sparrows often flip leaves or scratch with the feet to look for invertebrates. Birds disturbed by predators (or humans) may run, mouselike, through reeds or grasses, rather than take flight. When flushed, they usually do not fly far, alighting in a nearby shrub to observe the intruder.

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Low Concern

Populations of Swamp Sparrow have been fairly stable or have risen over the past half-century according to the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population at 23 million and rates them 6 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. Many North American wetlands have been drained and filled since the arrival of Europeans, so Swamp Sparrow populations may have declined substantially in the decades before the Breeding Bird Survey began. The long-term prospects of this sparrow will depend on wetland conservation.

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Ballentine, B., B. Horton, E. T. Brown, and R. Greenberg (2013). Divergent selection on bill morphology contributes to nonrandom mating between Swamp Sparrow subspecies. Animal Behaviour 86:467–473.

Bond, G., and R. E. Stewart (1951). A new Swamp Sparrow from the Maryland Coastal Plain. Wilson Bulletin 63:38–40.

Greenberg, R., K. M. Cammen, A. G. Wilson, B. J. Olsen, B. Ballentine, N. C. McInerney, and R. C. Fleischer (2016). Geographic population structure and subspecific boundaries in a tidal marsh sparrow. Conservation Genetics 17:603–613.

Lutmerding, J. A. and A. S. Love. (2020). Longevity records of North American birds. Version 2020. Patuxent Wildlife Research Center, Bird Banding Laboratory 2020.

Mowbray, Thomas B. (1997). Swamp Sparrow (Melospiza georgiana), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2019). The North American Breeding Bird Survey, Results and Analysis 1966–2019. Version 2.07.2019. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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