Marsh Wren

The Marsh Wren is a small wren, ranging from 10.4 and 14.0 cm in total length and weighing between 9.0 and 14.0 grams. Males and females have similar plumage. This species has a black crown, white superciliary stripes, warm-brown upperparts with faint black bars, a black and white striped triangular region on the upper back, buffy sides and breast, whitish below, and dark barring on the tail. Marsh Wrens have brown eyes, pale brown feet and legs, and a brownish bill. Males are larger than females, though body size varies geographically. Juvenile plumage is similar to adult plumage except there are fewer black markings on back, the superciliary stripe is faint or absent, and wings are only faintly barred (Kroodsma and Verner 1997).

Range mass: 9 to 14 g.

Other Physical Features: endothermic ; bilateral symmetry

Marsh Wrens use a variety of wetland habitats. Cattails and bulbrush is the vegetation that dominates most Marsh Wren habitat. This wren occurs in salt and brackish marshes in addition to freshwater sites. The habitat of the winter range is similar to that of the breeding range (Kroodsma and Verner 1997).

The breeding range of the Marsh Wren (Cistothorus palustris) extends west from the Atlantic coast to Nebraska and North from southern Illinois to northwestern. In the western United States C. palustris is a year round resident. There are also breeding and resident populations along coasts of the southern Atlantic and Gulf states. The wintering range extends south from the southwestern states of New Mexico, Arizona and Texas and into Mexico; Florida is also a wintering ground for Marsh Wrens (Kroodsma and Verner 1997).

Biogeographic Regions: nearctic (Native )

Marsh Wrens mainly eat invertebrates, especially insects (e.g. bees, ants, wasps, beetles, and moths) and spiders as well as aquatic invertebrates in freshwater marshes. Foraging occurs on or near the marsh floor; Marsh Wrens glean insects from stems and leaves of vegetation and the water's surface. Some birds may forage in thickets or shrub patches that occur near the marsh (Kroodsma and Verner 1997).

Unknown.

Systematics

There are two distinct groups of Marsh Wrens in North America and 14 subspecies. The two groups are divided into eastern and western populations largely on the basis of vocal characteristics, although there are differences in color, pattern, size and molt (Kroodsma and Verner 1997).

Perception Channels: visual ; tactile ; acoustic ; chemical

Habitat degradation is the greatest threat to Marsh Wren vitality, although some migrants are killed every year in collisions with communication towers and other structures. Destruction of marshes and wetlands used by Marsh Wrens as breeding or wintering grounds results in a great reduction in numbers in the area. Marsh Wrens readily colonize newly created or restored wetland habitats, however, resulting in increasing population sizes in some areas (e.g. high numbers of Marsh Wrens were found in marshes created by dam construction along the Colorado River) (Kroodsma and Verner 1997). Marsh wrens are a species of special concern in Michigan.

US Migratory Bird Act: protected

US Federal List: no special status

CITES: no special status

State of Michigan List: special concern

IUCN Red List of Threatened Species: least concern

Conservation concerns may prevent development of wetland habitat.

Marsh Wrens are polygynous, but the percentage of males mating with more than one female varies among populations (e.g. in Georgia 5% of males had more than one mate, while 41-54% of males in Manitoba had more than one female). Timing of pair formation is variable depending on population and year. Males begin singing within one to two days of their arrival on the breeding grounds. In migrant populations females usually arrive on breeding grounds seven to ten days after males and then mate with males a few days after their arrival.

Males build numerous, single-opening dome-shaped nests on their territory prior to female arrival. Female choice is dependent upon territory quality and nesting status of other females (i.e. females tend to prefer unmated males). When a female approaches a male's territory he flies over to her and sings. If she enters his territory the male will show her several nests he has constructed, and if she chooses to mate with the male she may line a nest with strips of grass, small stems, cattail downs, feathers and rootlets or she may build an entirely new nest (Kroodsma and Verner 1997).

Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous

Slightly smaller than the similarly-shaped Carolina Wren (Thryothorus ludovicianus), the Marsh Wren is most easily identified by its size (5 inches), white eye-stripes, and white-striped back. Other field marks include a curved bill, short tail, and short wings. Male and female Marsh Wrens are similar to one another in all seasons. The Marsh Wren has two distinct breeding populations, mainly differentiated by differences in song patterns. One breeds in the eastern U.S., south-central Canada, and along the Gulf Coast. The other breeds from the Pacific coast of the U.S. east to the western Plains. Most birds breeding in the northeastern U.S. and Canada migrate to coastal areas of the southeastern U.S. in winter, while some western birds winter in the desert southwest and in Mexico. Most western Marsh Wrens, as well as coastal-breeding birds in the east, are non-migratory. Appropriately, the Marsh Wren inhabits a variety of marshland and wet grassland habitats across North America. The majority of Marsh Wrens breed in freshwater marshes, but coastal birds inhabit brackish or saltwater marshes as well. This species eats a variety of insects found in the water, on the blades of marsh grasses, or in the air. Due to this species’ preference for heavily-vegetated marshland habitats, the Marsh Wren is often more easily heard than seen. Male Marsh Wrens may be seen singing while perched atop marsh vegetation. With the aid of binoculars, Marsh Wrens may be seen while partially hidden in the undergrowth, climbing stalks of grasses while foraging for food. Marsh Wrens may also be seen undertaking short flights above the grass. This species is primarily active during the day.

Threat Status: Least Concern

Marsh wrens inhabit freshwater and saltwater marshes, usually nesting in association with bulrushes, cattails, and sedges or on occasion in mangroves (Welter, 1935; Bent, 1948; Kale, 1965; Verner, 1965). Standing water from several centimeters to nearly a meter is typical of the areas selected (Bent, 1948). Permanent water is necessary to provide a food supply of insects necessary to maintain the birds and as a defense against predation (Verner and Engelsen, 1970). Deeper water and denser vegetation are associated with reduced predation rates (Leonard and Picman, 1987).

The marsh wren (Cistothorus palustris) is a common bird inhabiting freshwater cattail marshes and salt marshes. Marsh wrens breed throughout most of the northern half of the United States and in coastal areas as far south as Florida; they winter in the southern United States and into Mexico, particularly in coastal areas. Marsh wrens eat mostly insects, and occasionally snails, which they glean from the surface of vegetation. This species was formerly known as the long-billed marsh wren (Telmatodytes palustris).

Many populations of marsh wren are polygynous, with some males mating with two, occasionally three, females in a season, while the remaining males have one mate or remain bachelors. For example, Leonard and Picman (1987) found 5 to 11 percent bachelor males, 41 to 48 percent monogamous males, 37 to 43 percent bigamous males, and 5 to 12 percent trigamous males in two marshes in Manitoba, Canada. Similarly, Verner and Engelsen (1970) found 16 percent bachelors, 57 percent monogamous, and 25 percent bigamous males in eastern Washington state. In contrast, Kale (1965) found most males to be monogamous through 4 years of study in Georgia. Males arrive at the breeding marshes before the females to establish territories that include both nest sites and foraging areas (Kale, 1965; Verner, 1965; Welter, 1935). Males build several nests in their territories throughout the breeding season (Kale, 1965; Verner, 1965). The female usually only adds lining material to a nest of her choice, although some may help construct the breeding nest (Kale, 1965). Breeding nests are oblong in shape, with a side opening, and are woven of cattails, reeds, and grasses and lashed to standing vegetation, generally 30 cm to 1 m above standing water or high tide (Bent, 1948; Verner, 1965). Incubation lasts approximately 2 weeks, as does the nestling period (Kale, 1965; Verner, 1965). After fledging, one or both parents continue to feed the young for about 12 days (Verner, 1965). Many populations typically rear two broods per year, although some may rear three (Kale, 1965; Verner, 1965). In the more monogamous populations, both parents regularly feed young, but in the more polygynous ones, the females may provide most of the food, with males assisting only toward the end of the nestling period (Leonard and Picman, 1988; Verner, 1965).

Slightly smaller than the similarly-shaped Carolina Wren (Thryothorus ludovicianus), the Marsh Wren is most easily identified by its size (5 inches), white eye-stripes, and white-striped back. Other field marks include a curved bill, short tail, and short wings. Male and female Marsh Wrens are similar to one another in all seasons. The Marsh Wren has two distinct breeding populations, mainly differentiated by differences in song patterns. One breeds in the eastern U.S., south-central Canada, and along the Gulf Coast. The other breeds from the Pacific coast of the U.S. east to the western Plains. Most birds breeding in the northeastern U.S. and Canada migrate to coastal areas of the southeastern U.S. in winter, while some western birds winter in the desert southwest and in Mexico. Most western Marsh Wrens, as well as coastal-breeding birds in the east, are non-migratory. Appropriately, the Marsh Wren inhabits a variety of marshland and wet grassland habitats across North America. The majority of Marsh Wrens breed in freshwater marshes, but coastal birds inhabit brackish or saltwater marshes as well. This species eats a variety of insects found in the water, on the blades of marsh grasses, or in the air. Due to this species’ preference for heavily-vegetated marshland habitats, the Marsh Wren is often more easily heard than seen. Male Marsh Wrens may be seen singing while perched atop marsh vegetation. With the aid of binoculars, Marsh Wrens may be seen while partially hidden in the undergrowth, climbing stalks of grasses while foraging for food. Marsh Wrens may also be seen undertaking short flights above the grass. This species is primarily active during the day.

Marsh wrens consume aquatic invertebrates, other insects, and spiders, which they glean from the water surface, on stems and leaves of emergent vegetation, and the marsh floor (Kale, 1965; Welter, 1935). They sometimes also feed by flycatching (Welter, 1935). The insect orders most commonly taken include Coleoptera (both adults and larvae), Diptera (adults and larvae), Hemiptera (juveniles and adults), Lepidoptera (larvae most commonly fed to nestlings); and Odonata (newly emerged) (Bent, 1948; Kale, 1964). When feeding the young, at first the parents bring mosquito adults and larvae, midges, larval tipulids, and other small insects (Welter, 1935). As the young mature, the parents bring larger insects such as ground beetles, diving beetles, long- horned beetles, caterpillars, dragonflies, and sawflies to the nestlings (Welter, 1935). In a population in Georgia, spiders (usually 1 to 3 mm in size, sometimes 12 to 15 mm), small crabs (5 to 7 mm), small snails (1 to 3 mm), and insect eggs also were consumed and fed to nestlings (Kale, 1965). Thus, organisms that are aquatic for all or part of their lives are an important component of the diet of marsh wren adults and nestlings.

Singing in a marsh at Hammonasset Beach, Connecticut

The marsh wren (Cistothorus palustris) is a small North American songbird of the wren family. It is sometimes called the long-billed marsh wren to distinguish it from the sedge wren, also known as the short-billed marsh wren.