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Sedge Wren Life History

Habitat

Habitat Grasslands

Sedge Wrens nest in dense, tall growths of sedges and grasses in wet meadows, hayfields, retired croplands, upland margins of ponds and marshes, tallgrass prairie, coastal marshes, and sphagnum bogs—ideally all with some woody shrubs interspersed. It does not nest in tall reeds or deep-water marshes (generally habitat for Marsh Wren) and avoids sparsely vegetated wetlands that lack a shrub element. Migrants usually gravitate toward habitats that resemble nesting habitat, including agricultural fields, grasslands, saltmarshes, and overgrown weedy fields. Their winter ecology has not been studied extensively. In the southeastern U.S., they frequent sedge meadows, upland edges of marshes (salt, brackish, and fresh), pine savannas, palmetto prairies (especially in wet, boggy spots), old fields with broomsedge, and sometimes dry, grassy places with scattered shrubs and taller weeds.

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Food

Food Insects

Sedge Wrens eat spiders and insects, among them weevils, bugs, ants, ladybird beetles, locusts, crickets, grasshoppers, and caterpillars. They forage low in vegetation and on the ground, where their small size, long legs, and slender bill are excellent adaptations for foraging on insects in dense vegetation. Like most wrens, they probably also consume a small amount of seeds.

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Nesting

Nest Placement

Nest Shrub

Males construct multiple ball-shaped nests, woven from grasses and sedges, and place them on the ground or in vegetation (especially dense sedges), up to 39 inches above the ground.

Nest Description

From the nests begun by the male; the female chooses one and lines it with fine grasses, feathers, and fur. The additional nests might serve to distract predators or other wrens that might destroy eggs. Dimensions of the roughly spherical nest average 4.1 inches (exterior) and 2.2 inches (interior). The entrance hole, on the side of the nest, measures between 0.6 and 1.0 inches.

Nesting Facts

Clutch Size:3-8 eggs
Number of Broods:1-2 broods
Egg Length:0.6-0.7 in (1.44-1.73 cm)
Egg Width:0.4-0.5 in (1.12-1.27 cm)
Incubation Period:13-16 days
Nestling Period:12-14 days
Egg Description:

White and unmarked.

Condition at Hatching:

Naked and helpless.

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Behavior

Behavior Ground Forager

In North America, males arrive ahead of females and establish a territory for nesting and a territory for foraging. Sedge Wrens are somewhat mysterious birds, as they are both nomadic—abundant in a wetland one year, absent the next—and secretive. Some Sedge Wrens are monogamous; others are polygynous (having several female mates) or polyandrous (having several male mates). Sedge Wrens establish winter territories as well as breeding territories. Both sexes may destroy nests of nearby Sedge Wrens by piercing the eggs.

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Conservation

Conservation Low Concern

The North American Breeding Bird Survey estimates that Sedge Wren populations fell sharply between 1993 and 2015. They estimate an annual decline of 3.35% per year, which represents a 54% cumulative decline over that period. In a 2016 document, Partners in Flight estimated the U.S./Canada breeding population at 5.4 million. Sedge Wrens are scarce over much of their North American range, probably because of habitat requirements. Conservation threats include destruction of wetlands, including wet meadows, many of which have been lost since European colonization. Sedge Wrens nesting in hayfields often lose their broods to harvest; this could be ameliorated by delaying harvesting until the young have fledged. Like most songbirds that migrate nocturnally, Sedge Wrens frequently strike buildings and other structures and are killed.

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Credits

Burns, J. T. (1982). Nests, territories, and reproduction of Sedge Wrens (Cistothorus platensis). Wilson Bulletin 94:338-349.

Herkert, James R., Donald E. Kroodsma and James P. Gibbs. (2001). Sedge Wren (Cistothorus platensis), 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.

Rosenberg, K. V., J. A. Kennedy, R. Dettmers, R. P. Ford, D. Reynolds, J. D. Alexander, C. J. Beardmore, P. J. Blancher, R. E. Bogart, G. S. Butcher, A. F. Camfield, A. Couturier, D. W. Demarest, W. E. Easton, J. J. Giocomo, R. H. Keller, A. E. Mini, A. O. Panjabi, D. N. Pashley, T. D. Rich, J. M. Ruth, H. Stabins, J. Stanton, and T. Will (2016). Partners in Flight Landbird Conservation Plan: 2016 Revision for Canada and Continental United States. Partners in Flight Science Committee.

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. 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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