Smaller even than the Winter Wren (Troglodytes hiemalis), the Sedge Wren is most easily identified by its size (4-4 ½ inches), streaked head, and indistinct eye-stripes. Other field marks include a curved bill, short tail, and short wings. Male and female Sedge Wrens are similar to one another in all seasons. The Sedge Wren breeds across the northern Great Plains from central Canada south to Missouri and Illinois. Smaller numbers breed in the Great Lakes and east as far as New England. This species winters along the coast of the southeastern U.S.from Virginia to Texas, as well as into northern Mexico. Isolated non-migratory populations are found from southern Mexico south to southern Argentina. Sedge Wrens inhabit marshes and grasslands. In general, this species tends to live in drier parts of these habitats than the Marsh Wren (Cistothorus palustris), its close relative. Sedge Wrens mainly eat small invertebrates, including insects and spiders. Due to this species’ preference for heavily-vegetated habitats, the Sedge Wren is often more easily heard than seen. Male Sedge Wrens may be seen singing while perched atop vegetation. With the aid of binoculars, Sedge Wrens may be seen while partially hidden in the undergrowth, climbing stalks of grasses while foraging for food. Sedge Wrens may also be seen undertaking short flights above the grass. This species is primarily active during the day.
Sedge wrens are migratory, breeding in south central Canada and the north central United States and wintering in the southeastern United States, including the Gulf states and eastern Texas, and northeastern Mexico. There are some disjunct, resident populations in portions of Mexico. Northern breeding populations are found throughout the Great Lakes states, including Indiana, Iowa, Minnesota, the eastern Dakotas, Ontario, and southern Alberta, Saskatchewan, and Manitoba. Breeding also occurs in portions of Mexico, Central America, and throughout South America in appropriate habitat. Northern breeding populations winter along the Atlantic coastal plain from New Jersey to Florida, throughout the Gulf Coast states, eastern Texas, and into eastern Mexico to Veracruz.
Biogeographic Regions: nearctic (Native ); neotropical (Native )
- Herkert, J., D. Kroodsma, J. Gibbs. 2001. Sedge Wren (Cistothorus platensis). Birds of North America Online, 582: 1-20. Accessed May 21, 2009 at http://bna.birds.cornell.edu/bna/species/582.
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Breeding
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) BREEDING: eastern Alberta east across southern Canada to (formerly) central Maine and New Brunswick, south to eastern Arkansas, southern Illinois, central Kentucky, western West Virginia, and southeastern Virginia, west to Dakotas and Kansas (AOU 1983). Most common in Minnesota, Wisconsin, north-central Michigan, southern and central Manitoba, and the Lake of the Woods area of northwestern Ontario (Jalava 1993). In the northeastern U.S., tidewater marshes in New Jersey, Delaware, Maryland, and Virginia currently support the largest, most stable populations (Gibbs and Melvin 1992). NON-BREEDING: Tennessee and Maryland south to southeastern New Mexico and southeastern U.S. (AOU 1983); the most concentrated populations occur along the Gulf Coast of Texas and in Louisiana; other areas of abundance include the North Carolina coast, lowlands around Pensacola, the Pecos River area in western Texas, and the Green Swamp near Wilmington, North Carolina (Root 1988). RESIDENT: Middle and South America (south to western Panama; Colombia, Venezuela, and Guyana south in the Andes to Tierra del Fuego) (Hilty and Brown 1986), though southernmost populations are migratory.
Sedge wrens are smallm, black and brown streaked wrens. They have white bellies and throats, with soft brown on the sides, breast, and under the tail. The tails have black bars. They are from 10 to 12 cm and 7 to 10 g. Males and females are alike and there is no difference in plumage throughout the year, although males may be slightly larger in some features. Sedge wrens may be confused with other wren species, including marsh wrens (Cistothorus palustris), house wrens (Troglodytes aedon), winter wrens (Troglodytes troglodytes), Carolina wrens (Thryothorus ludovicianus), and Bewick's wrens (Thryomanes bewickii). They are distinguished by their striped heads and backs. They can also be distinguished by their songs.
There are 18 recorded subspecies of sedge wrens, divided into 3 "groups," each of which may deserve recognition as a species. The "stellaris" group (sedge wren) is found in North America and is primarily migratory. The "plantensis" group (western grass wren) is found in western South America, from Colombia and Venezuela to Tierra del Fuego. The "polyglottus" group (eastern grass wren) is found in eastern South America, from Colombia and Venezuela through Brazil to northern Argentina.
Range mass: 7 to 10 g.
Range length: 10 to 12 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike
Length: 11 cm
Weight: 9 grams
In contrast to marsh wrens (CISTOTHORUS PALUSTRIS), the only other wren occurring in eastern wetlands, sedge wrens lack a distinct white stripe over the eye, are lighter-colored, and have a shorter bill (Vickery 1983).
Sedge wrens, as their name suggests, are found in sedge meadows and other wet grasslands, such as the shorelines of ponds, marshes, bogs, and coastal wetlands. They can also be found in agricultural areas with similar qualities, such as hayfields and early successional oldfields. They prefer areas with dense cover of grasses and sedges, where they place their nests, and avoid open areas, cattail marshes, sparse vegetation, and flooded grasslands. They prefer areas with a moderate density of shrubs as well.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: savanna or grassland
Wetlands: marsh ; bog
Habitat and Ecology
Comments: BREEDING: Grasslands and savanna, especially where wet or boggy; sedge marshes; moist meadows with scattered low bushes; upland margins of ponds and marshes; coastal brackish marshes of cordgrass, herbs, and low shrubs; locally in dry cultivated grainfields (AOU 1983). Avoids cattail marshes. Sings from exposed perch, otherwise creeps and hops on or near ground in tall sedgy grass or wet tangles at the bases of shrubs (Colombia, Hilty and Brown 1986). Nests low in tall dense growths of sedges or grasses, or similar herbage, very near ground, or over shallow water (Harrison 1978).
Nesting areas may change opportunistically from year to year as conditions change. Several nests are built within a single breeding territory each season. Nesting takes place among dense, tall growths of sedges and grasses in wet meadows, hayfields, retired croplands, and upland margins of ponds and marshes. It also occurs in coastal, brackish marshes. Scattered shrubs and an absence of standing water are also typical features of nesting habitats. Highly sensitive to habitat conditions, and abandon sites rendered too dry by drainage or drought or too wet by flooding. Will also abandon sites if shrubs become too prevalent. Opportunistic breeders and may renest at different locations during the same breeding season. Usually do not occupy the same site for more than one to three years.
In South Dakota, preferred sites within landscapes dominated by grassland; size of individual breeding habitat patch was not as important as was its landscape context (Bakker et al. 2002).
In New England, Bagg and Eliot (1937) suggested that sedge wrens colonized wet meadows early in the nesting season but, due to summer drying, used permanently wet, tussocky marshland in July for renesting. Nesting has been reported in Maine from a variety of habitat types, including wet fields, bush-covered pastures, sedgy and grassy meadows, marshes, bogs, and thick, grassy areas on barren lands (Palmer 1949). Preferred habitats in tidewater areas in Maryland consisted of switchgrass (PANICUM VIRGATUM) meadows along the inner margins of tidal marshes (Stewart and Robbins 1958). In the Allegheny Mountains of Maryland, sedge meadows in boreal bogs were usually occupied, whereas orchard grass pastures and hayfields were used at upland sites elsewhere in the state (Stewart and Robbins 1958).
At moist soil impoundments in Missouri, associated with unflooded areas with rank or dense vegetative cover, and avoided short, sparse, or open vegetative cover, openings, and flooded areas (Fredrickson and Red 1986). In a large, marsh complex in Wisconsin, Manci and Rusch (1988) observed them primarily in habitats dominated by sedges (CAREX spp.), and secondarily in upland grasslands. Avoided areas of deepwater cattail (TYPHA spp.), shallow-water cattail, dry cattail, and river bulrush (SCIRPUS FLUVIATILIS).
In Minnesota, preferred dense sedge growth intermixed with patchy, one to two m high shrubs (Niemi and Hanowski 1984). Average vegetative characteristics territories in Minnesota were 303 sedge stems/meter squared, 16 forb stems/meter squared, 50 shrub stems/meter squared, and a predominant vegetation height of 1.1 m (Niemi 1985). Higher densities occurred in areas with medium shrub densities (11-32 stems/0.0025 ha) than in areas with more or less shrub growth (Niemi and Hanowski 1984). At another Minnesota site, major vegetation types in territories were stands of great bulrush (SCIRPUS ACUTUS), tussock sedge (CAREX STRICTA), and water sedge (C. AQUATILIS) and monotypic stands of C. AQUATILIS (Burns 1982).
At Delta Marsh, Manitoba, occurred in wet, white-top (SCOLOCHLOA FESTUCACEA) and sedge (CAREX ATHERODES) meadows (Picman and Picman 1980). Crawford (1977) studied them in a glacial marsh complex in Iowa, and found nests in drier sites around marshes in areas dominated by reed canary grass (PHALARIS ARUNDINACEA) (17 nests) and river bulrush (14 nests) stands. Reproductive success was higher, however, for males with territories consisting primarily of bulrush (SCIRPUS FLUVIATILIS). Similarly, Walkinshaw (1935) considered the portion of a marsh intermediate between deepwater sections and the bordering meadow to be preferred habitats in Michigan. Birds used areas where sedges and grasses predominated, with clumps of shrubs and herbaceous growth, and with no standing water.
In a Nebraska study, wrens avoided high ground and occurred most commonly along moist, ungrazed margins of relict channels (sloughs) where water sedge, common ragweed (AMBROSIA ARTEMISIFOLIA), and river bulrush predominated (Lingle and Bedell 1989). A southward-sloping hillside dominated by a mixture of rank grasses and weeds about one m high, interspersed with clumps of smooth sumac (RHUS GLABRA), supported a nesting population during a particularly wet year in Kansas (Tordoff and Young 1951).
NON-BREEDING: Little information is available on wintering habitats. Presumed similar to breeding habitat, but in migration and winter also in brushy grasslands (AOU 1983). Brackish and freshwater sedge meadows and marshes are used, as are old fields and prairies with dense, matted grass or weeds (Howell 1932). Drier portions of salt marshes may be used during migration (Forbush 1929, Palmer 1949).
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.
Migration occurs in September or October, depending on the region (Bent 1915, Walkinshaw 1935). Incidental kills at transmitting television towers in Florida suggest that most fall migration occurs in October, well after the migration of most warblers, vireos, and other, similarly sized passerines is underway (Taylor et al. 1983). Clustering of multiple wren species at tower kills indicates that sedge wrens migrate in flocks with other wrens (Taylor et al. 1983). In southern South America, migrates north for the austral winter.
Sedge wrens are invertivores, eating mainly insects and spiders. There is little information on details of their diet or foraging because of their cryptic habits, but a few observations suggest they mainly forage on the ground near the bases of grasses and sedges. Some stomach content analyses suggest that sedge wrens eat large proportions of spiders, along with ants, weevils, lady beetles, butterfly and moth larvae, and grasshoppers.
Animal Foods: insects; terrestrial non-insect arthropods
Primary Diet: carnivore (Insectivore , Eats non-insect arthropods)
Comments: Eats insects and spiders (Terres 1980); picks items from the ground or from foliage. Information on diet is limited. Howell (1932) examined 34 stomachs of sedge wrens overwintering in Florida and concluded that the diet consisted wholly of spiders and insects, including ants, bugs, weevils, ladybird beetles, moths, caterpillars, locusts, crickets, and grasshoppers. Seven stomachs of sedge wrens from Pennsylvania contained beetles and spiders (Warren 1890). Walkinshaw (1935) observed the birds feeding their young moths, spiders, mosquitos, flies, grasshoppers, and bugs.
The "mouse-like," inconspicuous foraging behavior (Howell 1932, Walkinshaw 1935) suggests that these birds forage mainly at ground level, probably for insects hiding in moist soil and among bases of sedges and grasses. Particular adaptations of sedge wrens to foraging in shrubby grasslands include their small size, relatively long bills, and longer pelves and legs in comparison to congeners using forested habitats (Niemi 1985). The abundance of insect food in frequented upland habitats is probably a function of rainfall, soil moisture, and productivity of adjacent marshlands. Aquatic insects characteristically move from wetlands following metamorphosis and seek refuge on nearby uplands (Orians 1980), where they may serve as an important food source.
Sedge wrens prey on invertebrates and are likely to be preyed on by small, terrestrial and avian predators. There are no reported parasites or diseases.
Sedge wren nests seem to be heavily preyed on, predation is the dominant reason for nest failure in some areas. However, few predators are reported. Red foxes are known to take sedge wrens. Responses to predators are unknown, but sedge wrens are cryptically colored and behave secretively.
- red foxes (Vulpes vulpes)
Anti-predator Adaptations: cryptic
Nesting territory size averages about 0.2 ha (Byrd and Johnston 1991). Forty weekly estimates of territory size for five males in Minnesota averaged 1,280 meters squared (Burns 1982). Densities (males per ten ha) of nesting birds have been reported as four in grazed areas and 12 in ungrazed areas in Nebraska (Lingle and Bedell 1989), 86 in Michigan (Walkinshaw 1935), 18 in Wisconsin (Manci and Rusch 1988), 12 in Illinois (Birkenholz 1984), 15 in North Dakota (Higgins et al. 1984), 19 in Minnesota (Hanowski and Niemi 1986), three in Kansas (Cink and Sepahi 1983), seven in Iowa (Wilson 1983), and three in Maryland (Stewart and Robbins 1958). May destroy the eggs of other sedge wrens or other small birds.
Habitats are characterized by vegetation types and soil moisture regimes that are highly susceptible to drying or flooding caused by annual and seasonal variation in rainfall. Vegetative succession and disturbance by grazing, haying, and planting also impart a highly transitory character to nesting habitats. This habitat instability may lead to the high mobility and low site tenacity of sedge wrens (Kroodsma and Verner 1978). The complete regional absence in some years, however, suggests that some factor in addition to habitat instability is involved in population fluctuations, perhaps regional patterns of rainfall (Cody 1985) or weather conditions during migration. The nature of the communication system as a unique adaptation to high population mobility (Kroodsma and Verner 1978) suggests that opportunistic breeding and low site tenacity has occurred for a long time, rather than being of recent origin, such as in response to agriculture and habitat loss (Burns 1982). These birds are "curiously local" and occur sporadically within the Andean Zone of South America, and there is no reason to believe that anthropogenic factors influence the species' distribution there (Fjeldsa 1988).
Life History and Behavior
One of the few natural history aspects of sedge wrens that have been well studied are their vocalizations and much is known about song development. Sedge wren males develop from 29 to 63 individual song types through improvisation. Songs are not strictly learned or imitated from songs encountered in their environment, rather they are improvised by individual males to be unique. This is in contrast to closely related marsh wrens (Cistothorus palustris), which use songs primarily learned from the environment. Patterns seem to differ in resident populations of sedge wrens in Central and South America, where there is more evidence of song learning or imitating nearby conspecific males, rather than improvisation. Only males sing, they begin developing song as fledglings, but then cease singing until the following year, when they develop their song repertoire.
Songs have been described as "staccato chattering." All sedge wren songs begin with a stereotyped set of 3 to 4 notes, followed by various trills that vary individually. Marsh wren calls can be distinguished because of their more musical quality and less emphasis on the initial, stereotypes portion of the song sequence. Males may begin to sing on their wintering grounds in the spring, but their arrival on breeding grounds is generally discovered through the detection of singing males. Males sing from perches, usually, but will sing at other times as well. Males repeat individual song types on average 19 times before switching to another song type, although this varies substantially. Social context changes how frequently males change between song types and how many types of songs they use. Competition with nearby singing males tends to increase the number of songs and the number of types of songs expressed.
Communication Channels: acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Lifespan in sedge wrens is not known, no banded sedge wrens have been recovered. Nests and adults are destroyed during hay and rice harvesting and by cattle trampling in pastures. Sedge wrens have also been reported colliding with towers during migration.
Many aspects of sedge wren natural history are not well studied and there is little information on how mated pairs form. It is thought that pairs form on the breeding grounds, males arrive up to 2 weeks before female to establish nesting territories. Males may have a single female mate or may attract multiple (usually just 2) females to their breeding territory.
Mating System: monogamous ; polygynous
Migratory populations of sedge wrens seem to have a nomadic breeding cycle. Northern breeding populations breed from May through June. Breeding then occurs in the southern United States from July into September, coinciding with the departure of northern breeding populations. This suggests that sedge wrens migrate to their northernmost breeding range for their first nesting, then migrate farther south to nest again. The later breeding season could also be late arrivals or an adaptive response to habitat quality in the southern portion of the range.
Females arrive on the breeding grounds after males and nest building begins within 2 weeks after male arrival. Males build several globular nests made of grasses and then females choose among them and line them with fine materials. Nests are built in dense stands of sedges or grass, in small shrubs, or on the ground at the base of dense vegetation. Nest height above ground ranges from 10 to 100 cm. Nests take 7 to 8 days to build, duplicate nests may be predator decoys or can be used by secondary female mates. In one study males had an average of 7.4 nests in their territories. Sedge wrens attempt single broods in some areas, but observations of double broods are reported from other areas. Monogamous pairs have a higher likelihood of attempting 2nd broods. Females lay 2 to 8 smooth, white eggs, laying 1 egg each day while they are lining the nest, and begin incubating at the last egg laid. Incubation is for 13 to 16 days and the young fledge at 11 to 16 days after that (usually 12 to 14). Young sedge wrens become independent some time after fledging, although how long they remain dependent on females after fledging is unknown. It is likely that sedge wrens breed in their first year after hatching, as do other wrens.
Breeding interval: Sedge wrens may have multiple broods in a breeding season. Double broods are known from some areas and these wrens may migrate south for another breeding attempt before the summer is over.
Breeding season: Sedge wrens breed from May into September in North America, although the timing of breeding varies latitudinally, earlier in the northern and later in the south. Breeding season in the southern hemisphere is unknown.
Range eggs per season: 2 to 8.
Range time to hatching: 13 to 16 days.
Average time to hatching: 13.8 days.
Range fledging age: 24 to 32 days.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Females incubate the young, which are born naked and helpless. Their eyes open at 4 days and they fledge at 11 to 16 days old. Young of secondary females lag behind the young of primary females in development. Females also provide all food for the young, although males may occasionally help. The young remain near the nest and are fed by their mother for some time after fledging. Males contribute to territory defense, so may help to protect young from predators.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Female, Protecting: Male, Female)
- Herkert, J., D. Kroodsma, J. Gibbs. 2001. Sedge Wren (Cistothorus platensis). Birds of North America Online, 582: 1-20. Accessed May 21, 2009 at http://bna.birds.cornell.edu/bna/species/582.
CHRONOLOGY: Nesting phenology may be related to site latitude and often occurs in two "waves" during a given season. Arrive at nesting areas as early as mid-April (Bent 1948) in some regions or as late as July in others (Lingle and Bedell 1989), and have been observed nesting as late as the end of September (Schwilling 1982). Nesting in many northeastern states is not initiated until July. In more northerly latitudes, nesting may be initiated from May to June, e.g., in North Dakota, Wisconsin, Minnesota, and Michigan, and again in late July through August, whereas in more southerly areas, e.g., Kansas and Arkansas, nesting may not be initiated until the latter period (Lingle and Bedell 1989). Late nesting at certain sites could represent renesting attempts by birds arriving from elsewhere or could be an adaptive response of local birds to delayed availability of moist, but unflooded, grassland habitats. Peak nesting populations in mixed-grass prairie in North Dakota occurred after unusually wet springs, but nesting activity showed little response to spring temperature (Cody 1985). Occupancy of a given site varies among years, and sites used one year may be abandoned the next (Palmer 1949, Burns 1982).
COURTSHIP AND BREEDING BEHAVIOR: Upon arrival at nesting areas, males establish territories that are used for courtship, nesting, and foraging (Burns 1982). Territory boundaries are fluid throughout the nesting season, and males may shift their activity and defend new areas as the season progresses. Males defend territories and attract mates by singing vigorously throughout the breeding season, as much as 22 h/day and at rates of up to 12-15 songs/min (Walkinshaw 1935, Kroodsma and Verner 1978). This combination of song components may permit mixing of highly dispersive populations (Kroodsma and Verner 1978) and may represent an evolutionary compromise between species identification and sexual selection among individuals. Because local dialects would be swamped in such highly mobile populations, neighboring males do not share song-type repertoires nor do they counter-sing by matching song-types (cf. marsh wren).
NESTING: Male CISTOTHORUS wrens build multiple, domed nests that figure prominently in courtship, and may also serve as dormitories and decoys for predators (Verner 1965, Picman and Picman 1980, Burns 1982). In Minnesota, males built an average of 7.4 complete nests and 0.8 incomplete nests on each territory (Burns 1982). Nests used for incubating eggs are built closer to the ground than dummy nests (Walkinshaw 1935) and have a substantial inner lining of grass, sedge, and feathers added by the female (Burns 1982).
Females begin laying one egg daily about the third day of nest lining (Burns 1982), and initiate incubation before the clutch is complete. Usually 7 eggs are laid per clutch (range is 2 to 8), although clutches laid later in the season may be smaller than earlier clutches (Bent 1948, Harrison 1978, Burns 1982). Clutch size 4 in Costa Rica (Stiles and Skutch 1989). Incubation is by the female only and lasts about 14 days (Burns 1982).
Females in some populations are double-brooded (Walkinshaw 1935, Burns 1982), but are single-brooded in others (Crawford 1977). Males may be serially or simultaneously polygynous and females may be serially polyandrous (Crawford 1977, Burns 1982). Mates of monogamous males had higher reproductive success than both primary and secondary females mated with polygynous males, whereas polygynous males had higher reproductive success than monogamous males (Burns 1982).
Nest success (nests with at least one egg hatching) was reported at 68% (n = 31 nests, Crawford 1977) and 69% (n = 18 nests, Burns 1982). Sources of nest loss include predation, infertile clutches, heavy rains, trampling by grazing cattle, and nest destruction by other sedge wrens (Walkinshaw 1935, Crawford 1977, Picman and Picman 1980, Burns 1982). The nestling period lasts 13-14 days (Walkinshaw 1935, Crawford 1977). Fledging success (number of young fledged per number of eggs laid) has been reported at 0.67 in Minnesota (Burns 1982). Virtually all parental care of nestlings is provided by the female, although males occasionally feed nestlings (Walkinshaw 1935, Burns 1982). Nest-building and continual defense by males of territories with abundant food may compensate females for a lack of male parental care of offspring. Fledglings move about in small groups until migration occurs (Gibbs and Melvin 1992).
Molecular Biology and Genetics
Barcode data: Cistothorus platensis
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Cistothorus platensis
Public Records: 12
Specimens with Barcodes: 12
Species With Barcodes: 1
Sedge wren populations shows small increases between 1966 and 1996, but sedge wrens have suffered from the loss of mesic grasslands throughout their range and local populations have experienced declines as a result. Wet grasslands are frequently drained and converted to agriculture, making them less suitable for sedge wrens. Also, grazing, burning, and mowing, sometimes used to manage grasslands for other species, negatively effects sedge wrens because they prefer tall, dense grasslands. Overgrazing and burning in Argentina have resulted in severe population declines of sedge wrens. They are considered "least concern" by the IUCN because of their wide range, large estimated population sizes, and lack of evidence for substantial population declines. However, the U.S. Fish and Wildlife Service considers them a U.S. migratory species of concern and they are listed as endangered, threatened, or special concern in 9 eastern and midwestern United States, including Pennsylvania, Massachusetts, New York, and New Jersey. Their erratic and seasonal occurrence in areas makes it difficult to accurately assess population sizes. Populations seem to do well in years with lots of precipitation.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
IUCN Red List Assessment
Red List Category
Red List Criteria
National NatureServe Conservation Status
Rounded National Status Rank: N5B - Secure
Rounded National Status Rank: N4B,N5N : N4B: Apparently Secure - Breeding, N5N: Secure - Nonbreeding
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Comments: Decline presumably has been due to loss and degradation of wetlands (Ehrlich et al. 1992), caused by suburbanization, intensive agricultural development, and natural succession. These factors and drought have resulted in declines in the northwestern part of the range (Jalava 1993). Loss of nesting habitat may be the major cause of declines in populations. About 4.75 million acres (1.92 million ha) of palustrine emergent wetlands, which include wet meadows important to nesting, were lost in the U.S. between the mid-1950s and mid-1970s (Tiner 1984). Preferred wetlands, such as sedge/grass meadows with moist or saturated soils, are the most easily drained and filled and are the wetland type most frequently destroyed by agriculture and urbanization (Tiner 1984). Substantial losses of grassland habitats in the northeast to urbanization and vegetative succession are evident. In just ten years (late 1960s-70s) along woodcock survey routes in all northeastern states combined, the availability of abandoned and active fields declined by 23- 25%, whereas the amount of land in young forest increased by 63% and that in urban/industrial uses increased by 33% (Dwyer et al. 1983). Clean-farming of wet fields (i.e., establishment of crop monocultures) was suggested as a primary cause of declines in the midwest region (Tate and Tate 1982). Aside from direct habitat loss, habitat disturbance such as late-summer burning of tidewater marshes in Maryland and livestock grazing (Walkinshaw 1935, Lingle and Bedell 1989) are considered threats to nesting. Regional reductions of the water table due to extensive urbanization in the Northeast may prevent occurrence of water "ponding" in fields, which creates the preferred wet-meadow habitat, and also may increase rates of vegetative succession. Wetland loss often leads to drying processes on adjacent upland habitats, and may ruin nesting habitats for wrens, which prefer to nest at moist upland margins of wetland patches. Severe weather conditions during winter could result in heavy mortality and influence population levels (Griscom 1949). Considerable mortality of migrant wrens has been observed at television towers throughout the eastern U.S. (Taylor et al. 1983). In the Argentine Pampas, overgrazing by cattle, soil compaction, and fires have eliminated tall grass habitats and have led to severe declines in populations (Bucher and Nores 1988). No information is available concerning the extent to which disease, parasites, predation, competition, or contaminants may limit populations.
Restoration Potential: A lack of information about reproductive potential and population structure precludes making any definitive statement concerning population management potential. The large clutch sizes (up to eight eggs) and potential ability to raise two broods per year (although unlikely in the Northeast), suggests high management potential. Because of high mobility, these birds can readily colonize new nesting areas. High mobility also confers high rates of genetic mixing upon populations, and thereby offsets some of the genetic problems facing the recovery of a severely diminished population. They will nest in a variety of grassland habitats, including wet meadows, marsh margins, bogs, and restored prairies (Higgins et al. 1984). Given an expanded and more stable habitat base and a long period without severe climatic events (hard winters or droughty summers), an increase in populations in the northeastern states seems possible (Gibbs and Melvin 1992).
Preserve Selection and Design Considerations: Lands preserved as nesting habitats should have dense, tall growths of sedges and grasses. Wet meadows and grassy upland margins of ponds, marshes, streams, rivers, hayfields and retired croplands, and brackish marshes represent high priority areas for protection. Other features of protected lands should include a scattering of shrubs and no standing water. Prefer breeding sites within large areas dominated by grassland; size of breeding habitat patch is not as important as its landscape context (Bakker et al. 2002).
Breeding sites should be protected from both drought conditions and flooding, and from fire, grazing, and human activity during the nesting season (May to August). Protected areas should be of sufficient size (e.g., more than five ha) to reduce area-related effects on nest predation (Burger 1988). Preserves should be buffered against an influx of pesticides from adjacent agricultural areas. Wetland areas adjacent to nesting areas should be preserved to prevent drying of upland margins and to retain sources of insect prey.
Management Requirements: Preservation of nesting habitat and maintenance of a complex of potential habitats throughout the Northeast is perhaps the most pressing management need. Particular attention should be directed toward safe-guarding nesting habitats at tidewater marshes in New Jersey, Delaware, Maryland, and Virginia, which currently support the largest, most regularly occurring populations in the northeastern U.S. Flooding will destroy nesting habitat as readily as drainage, and should be prevented during the nesting season. Overgrazing can easily eliminate the tall, rank cover on moist sites upon which sedge wrens depend.
Habitat preservation in the Northeast will depend on management programs that focus specifically on the sedge wren, and protection and management of populations on state and other public lands is suggested. Because of the sporadic and mobile nature of nesting, conservation will also depend on voluntary protection of nesting areas by private landowners. Given the small and transitory nature of populations, however, management to protect specific sites may have a low probability of attracting and holding sedge wrens; rather, extensive efforts over wide geographic areas may be necessary to have significant effects on regional populations.
GRAZING: Livestock grazing influences the structure and composition of plant cover and the supply and availability of invertebrate foods. Grazing animals should be excluded from meadows used by sedge wrens during the nesting season, although controlled grazing at other times of the year may be a means of beneficial meadowland management. Wrens nested at lower densities in grazed than ungrazed areas due to a reduction in vegetation stature caused by trampling and grazing by cattle (Lingle and Bedell 1989). BURNING: Fire can be used to stop encroachment of woody plants at nesting areas and to regenerate stands of tall grasses and sedges that provide needed cover. Prescribed burning should be restricted to the nonbreeding season. Habitat blocks should be managed in rotation to ensure annual availability of nesting habitat. For a useful overview of management of grassland and agricultural ecosystems for nongame wildlife such as sedge wrens, see Ryan (1986).
Management Research Needs: Initiate standardized survey programs in areas with established nesting populations (tidewater marshes of New Jersey, Delaware, Maryland, and Virginia) and coordinate and encourage birdwatchers and professional ornithologists to search for and record nesting activity elsewhere in the northeastern region throughout the summer season (May-August).
Conduct detailed studies of the habitat requirements in the Northeast to determine preferred soil moisture regimes, vegetation height, density, composition, specific cover requirements for nesting, and minimum effective habitat area.
Conduct a detailed study of the nesting biology in the northeastern U.S. (most information currently comes from Midwest populations) to determine nesting phenologies, extent of polygamy, ability to renest, causes of reproductive failure, causes and rates of mortality in juveniles and adults, juvenile dispersal and philopatry, and diet. Such studies will probably be most successful if conducted at sites with relatively long-established, reliable use by breeding wrens.
Conduct detailed studies of relationships between habitat use and abundance of invertebrate foods, including relationships between invertebrate populations and soil moisture, rainfall, wetland proximity, and grassland type.
Identify major stopover sites and overwintering areas in the northeastern and southeastern U.S.
Determine effects of disease, parasites, predators, weather, and contaminants on reproduction and populations, and monitor contaminant levels in the birds and their eggs in industrialized and agricultural portions of the Northeast.
Needs: The U.S. Fish and Wildlife Service's responsibility for reviewing wildlife habitat attributes of properties foreclosed by the Farmers Home Administration (U.S. Department of Agriculture) presents an opportunity to acquire and preserve grassland habitats in the northeastern states (Gibbs and Melvin 1992).
Relevance to Humans and Ecosystems
There are no adverse effects of sedge wrens on humans.
Sedge wrens are unique members of wet grassland ecosystems throughout the Americas.
Stewardship Overview: Breed in scattered localities throughout the Northeast, but are most abundant along the tidal marshes of the middle Atlantic states. They also nest along the upland margins of freshwater ponds and marshes, and among the grasses in wet meadows and hayfields. Nesting sites must be moist, and are readily abandoned if flooding or drying occurs. Loss of wet meadows is the most serious threat to populations. Management of wetland borders at wildlife management areas, however, could help to bolster local populations. The wren's high mobility could also help to disperse birds to uninhabited areas (Gibbs and Melvin 1992).
Regional population trends indicate a stable population in the Northeast, although existing surveys may undersample populations because territory establishment and nesting often do not occur until July (Gibbs and Melvin 1992).
Monitoring programs should extend through the summer in order to accurately survey sedge wrens. Although habitat loss seems to be a major factor in population declines, many authors have noted that populations seem well below the level that available habitats could support (Palmer 1949, Laughlin and Kibbe 1985, Andrle and Carroll 1988). Thus, although regional populations may now be stationary (as indicated by Breeding Bird Survey trends), individuals may be too sparsely distributed to effect any substantive or rapid population recovery. Preservation and maintenance of complexes of breeding habitat is needed; habitat management across wide geographic areas may be necessary to significantly enhance regional populations (Gibbs and Melvin 1992).
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The sedge wren (Cistothorus platensis) is a small songbird of the wren family. It was formerly known as the short-billed marsh wren, and in South America is often known as the grass wren. There are about 20 different subspecies which are found across most of the Americas. Some of these forms may be separate species that could be split in the future.
Adults have brown upperparts with a light brown belly and flanks and a white throat and breast. The back has pale streaks. They have a dark cap with pale streaks, a faint line over the eye and a short thin bill. They are one of the smallest species of wren at 10–12 cm (3.9-4.7 in) and 10-12 grams (0.35-0.4 oz).
In North America, their breeding habitat is wet meadows and marsh edges of eastern North America and central Canada. The nest is a round lump attached to low vegetation, entered from the side; it is usually well-hidden. The male often builds several unused nests in his territory; he may puncture the eggs of other birds nesting nearby. In South America, they are associated with very different habitats, principally páramo at very high elevations (3000 meters and above).
These birds forage low in vegetation, sometimes flying up to catch insects in flight. They mainly eat insects, also spiders.
The song of the male in North American populations is a rattling trill. The song of Central and South American forms is far more variable.
A sedge wren singing in restored tallgrass prairie habitat in Minnesota, US
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This bird's numbers are declining, possibly due to habitat loss.
Names and Taxonomy
Comments: Formerly known as Short-billed Marsh-Wren. Composed of three groups: STELLARIS (Sedge Wren), PLATENSIS (Western Grass-Wren), and POLYGLOTTUS (Eastern Grass-Wren) (AOU 1998). Constitutes a superspecies with C. MERIDAE and C. APOLINARI (AOU 1998).