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Thryothorus ludovicianusCarolina wren

By Kari Kirschbaum and Meredith Kurpinski

Geographic Range

Carolina wrens are year-round residents of the southeastern United States. The distribution of this species stretches from the Atlantic seashore to as far west as Texas, Nebraska, Kansas and eastern Oklahoma. It is bounded in the north by southern Michigan, New York, Massachusetts, and in extreme cases, Ontario Canada. The species has trickled as far southward as the northeast corner of Mexico and the Yucatan Peninsula, as well as parts of Central America. In unprecedented cases, Carolina wrens have been recorded as far west as New Mexico and Colorado, and as far north as Quebec, New Brunswick, and Maine. (Cornell Lab of Ornithology, 1999; Haggerty and Morton, 1995)

Habitat

Carolina wrens inhabit a wide variety of habitat types from brushy clearcuts to wooded swamps. Moist woodlands are a preferred habitat type, and moderate to dense shrub or brushy cover is an important habitat requirement. Examples of Carolina wren habitats include wooded riparian zones, wooded swamps, thickets, shrubbery, undergrowth, masses of logs, decaying timber, farmyards, forests, suburban gardens, live oak and palmetto hummocks, isolated clumps of trees in prairies, and old sheds. (Cornell Lab of Ornithology, 1999; Haggerty and Morton, 1995; Hill Collins, Jr. and Boyajian, 1965)

Physical Description

Carolina wrens are small birds, though they are large relative to other wrens. They weigh about 20 g and are 12 to 14 cm long. Carolina wrens have a deep rusty-brown back and a lighter cinnamon-colored underside that is unbarred. The throat and chin are white, and the wings, tail and undertail are barred black (in addition to white barring on the wings). This distinct coloring along with a distinctive broad white stripe above each eye distinguish Carolina wrens from other wren species. Carolina wrens have long, thin, slightly decurved bills with a dark upper mandible and a light-yellow lower mandible. Their legs are pink, and their tails are relatively long.

Male and female Carolina wrens are very similar, though males are, on average, slightly heavier. Males often have somewhat more prominent features, including longer bills, wings and tails. Juveniles are very similar to adults, with slightly lighter plumage.

Four subspecies of Thryothorus ludovicianus are recognized by the American Ornithologists' Union. These subspecies are largely distinguished by size, plumage and geographic variation. (Cornell Lab of Ornithology, 1999; Haggerty and Morton, 1995; Hill Collins, Jr. and Boyajian, 1965; Sauer, 1997)

  • Sexual Dimorphism
  • sexes alike
  • male larger
  • sexes shaped differently
  • Average mass
    20 g
    0.70 oz
  • Average mass
    17.5 g
    0.62 oz
    AnAge
  • Range length
    12 to 14 cm
    4.72 to 5.51 in

Reproduction

Carolina wrens are monogamous. Breeding pairs remain together for many years until one member of the pair dies or disappears. Male Carolina wrens put on an elaborate show in order to attract a mate. Their courtship involves encircling a female wren in a stiff, hopping, pattern while puffing out the feathers and fanning the tail. Occasionally a male will bring an offering of food to entice the female. (Cornell Lab of Ornithology, 1999; Haggerty and Morton, 1995; Hill Collins, Jr. and Boyajian, 1965)

Carolina wrens breed between March and October. Both members of a breeding pair work together to build a suitable nest. Nest construction takes place in the morning hours, and lasts up to one week. The first nests of the season are often larger and more time consuming than later nests. Carolina wrens will build their nests in a wide variety of natural and artificial sites. These include upturned roots, tree stumps, vine tangles, conifer branches, overhangs, abandoned woodpecker holes, boxes, tin cans, old shoes, mailboxes, old articles of clothing and furniture, window sills and coffee pots. The nests are usually built of twigs, grasses, weeds, leaves, mosses, pine needles, bits of bark and found objects such as hair, string, feathers, etc. The average nest is 8 to 23 cm long and 8 to 15 cm wide, and is usually less than 1.8 m above the ground. Nests are not reused for additional broods.

Females lay 3 to 7 (average 4) eggs at a rate of one per day. Eggs are usually laid within 1 to 2 hours of sunrise. Egg laying can begin as early as March in southern populations, and can continue through the summer. Carolina wrens nesting in the northern part of the range generally raise two broods per year, while pairs in the souther part of the range can raise up to three broods. Eggs are generally light cream to pinkish-white and spotted with dark purple to brown flecks near the ends of the egg. Carolina wrens' eggs are oval shaped and about 18 mm long.

The female incubates the eggs for 12 to 16 days. Meanwhile, the male spends his time gathering and delivering food to the female. The eggs usually hatch within one hour of each other. The newly hatched young have closed eyes (which open in three days), pale gray down, translucent pink skin and a yellow bill. They are fed immediately upon emerging.

During the first four days after hatching, the young are brooded intensively by the female. After this, the female continues to brood the young at night. The young are fed butterfly and moth larvae, crickets, grasshoppers and beetles by both parents.

The chicks leave the nest 12 to 14 days after hatching. After much coaxing from parents (for instance, adults will decrease food deliveries) the young depart the nest by hopping and flying erratically. The parents continues to visit the young, who remain together, for feeding purposes for weeks after they depart. The young become independent about 4 weeks after fledging. The young Carolina wrens are able to breed the first spring following their birth. (Cornell Lab of Ornithology, 1999; Haggerty and Morton, 1995; Hill Collins, Jr. and Boyajian, 1965)

  • Breeding interval
    Carolina wrens may raise up to three broods per summer.
  • Breeding season
    Carolina wrens breed between March and October.
  • Range eggs per season
    3 to 7
  • Average eggs per season
    4
  • Average eggs per season
    5
    AnAge
  • Range time to hatching
    12 to 16 days
  • Range fledging age
    12 to 14 days
  • Average time to independence
    4 weeks
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Carolina wrens share parental care. Both members of a breeding pair build the nest and feed the young. The female does all of the incubating of eggs and brooding of young. Meanwhile, the male brings food to the incubating female. (Cornell Lab of Ornithology, 1999; Haggerty and Morton, 1995; Hill Collins, Jr. and Boyajian, 1965)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
  • pre-hatching/birth
    • provisioning
      • male
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female

Lifespan/Longevity

The oldest known Carolina wren lived at least 6 years and 1 month. (Haggerty and Morton, 1995)

Behavior

Carolina wrens are diurnal and non-migratory. Breeding pairs defend a territory year-round, using songs and calls to advertise their occupancy.

Carolina wrens are essentially terrestrial. They spend the majority of their time hopping, sometimes at surprisingly high speeds, along the ground. While they are capable of short and erratic flight, they do not usually fly far. They will, however, use their wings to assist in leaps over tree stumps and debris piles. In addition, Carolina wrens are capable of hitching themselves up trees for nest building or feeding.

Carolina wrens can be found preening in a wide variety of settings, including open tree branches. They utilize their bills and wings to preen, and have been observed dust-bathing. Preening is often accompanied by sun-bathing. (Haggerty and Morton, 1995; Hill Collins, Jr. and Boyajian, 1965)

  • Range territory size
    0.01 to 0.081 km^2

Home Range

One study in Alabama estimated the average home range of Carolina wrens to be 0.007 square kilometers. (Haggerty and Morton, 1995)

Communication and Perception

Carolina wrens communicate using physical displays and vocalizations. Examples of physical displays employed by Carolina wrens include courtship displays (described in "Mating Systems") and agonistic displays that involve holding the body horizontal with the wings held out, the tail fanned and the head and bill pointed at the intruder. Physical displays are often accompanied by vocalizations.

The song of Carolina wrens is loud and high pitched. It consists of varied sounds including: trills, clacks, chatters (mostly used by females) and rattles. Songs normally contain 3 to 5 identical syllables, each containing 2 to 12 notes. The frequency has an average range of 1.8-4.5 kHz. The phonetic translation of these songs has been described as: TEA-kettle, TWEEdle, SWEETheart, CHE-wortle, and CHOO-wee. While females produce the basic sounds, only male Carolina wrens produce songs. The sounds and songs of this species can be used in a number of situations. A few of these instances include: to threaten a predator or another wren, in interspecific mobbing, during territorial defense, to indicate mood, for appeasement between mates, as a "distress" call, to differentiate rivals by sex, etc. Carolina wrens sing at all times of the year and all times of the day, but they are heard most frequently during late winter and early spring. (Cornell Lab of Ornithology, 1999; Haggerty and Morton, 1995; Hill Collins, Jr. and Boyajian, 1965; Sauer, 1997)

Food Habits

Carolina wrens are ground-foraging insectivores. They eat a large variety of insects and spiders opportunistically, without showing much preference. Carolina wrens search for food by using their bills to move brush and vegetation, to search under brush piles, in masses of logs and decaying timber, under upturned roots, under tree bark, and around the banks of swamps. As ground feeders, Carolina wrens are vulnerable to harsh winters. During long winters, this species is often forced to retreat to man-made feeding stations and brush piles. Though they primarily feed on the ground, Carolina wrens may also be seen climbing tree trunks in a manner similar to creepers, prying under bark and in crevices.

A study of the stomach contents of 291 Carolina wrens found that 94% of the food was animal matter, while the remaining 6% was vegetable matter. The stomach contents broke down as follows: 22% caterpillars and moths, 19% bugs (including stick bugs, soldier bugs, leaf-legged bugs, leaf hoppers, and chinch bugs), 14% beetles (including ground beetles, weevils, cucumber beetles, bean leaf beetles, and flea beetles), 13% grasshoppers, crickets, and cockroaches, 11% spiders, 5% ants, bees, and wasps, 3% flies. Millipedes, sowbugs, snails, and cotton-boll weevils made up a small percentage of stomach contents. In a few rare instances, lizard, frog and snake remains were also found. The 6% vegetable matter was composed of bayberry seeds, sweet gum, poison ivy, sumac, acorn mast and weeds. (Cornell Lab of Ornithology, 1999; Haggerty and Morton, 1995; Hill Collins, Jr. and Boyajian, 1965)

  • Animal Foods
  • amphibians
  • reptiles
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • Plant Foods
  • seeds, grains, and nuts
  • fruit

Predation

Predation of adult carolina wrens has not been documented. However, birds such as blue jays, Cooper's hawks and sharp-shinned hawks are likely predators.

Carolina wren eggs and nestlings are vulnerable to predation by raccoons, black rat snakes, gray squirrels, mink, gray foxes and eastern chipmunks.

When approached by a predator, Carolina wrens may call in alarm or chase after the predator, sometimes pecking at it. (Haggerty and Morton, 1995)

Ecosystem Roles

Carolina wrens affect the populations of the insects and spiders they eat, and provide valuable food for their predators. They compete with other cavity-nesting species for nest sites. They also provide habitat for various parasites, including mites, lice, ticks, and blowfly larvae. (Haggerty and Morton, 1995)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

We do not know of any way in which Carolina wrens affect humans.

Economic Importance for Humans: Negative

There are no known negative effects of Carolina wrens on humans.

Conservation Status

Because Carolina wrens are highly adaptable and able to inhabit a range of habitats, this species is common and widespread. With an estimated global population of 17,000,000 individuals, this species is thriving, and its range is increasing. Humans do manage for Carolina wrens in the northern part of their range where harsh winters can severely impact populations. During harsh winters, conservation organizations may place nest boxes in the wrens' habitat to aid in survival. These boxes are used for roosting and nesting. (Haggerty and Morton, 1995)

Other Comments

There are four sub-species of the Carolina Wren. The first, T.l. ludocavicianus is found in the northern regions and is generally found as far south as Florida and southern Texas. T.l. miamensis can be found mostly in Florida. T.l. burleigh inhabits islands off the coast of Mississippi. The fourth sub-species, T.l. lomitensis can be found mainly in parts of Texas. (Haggerty and Morton, 1995)

Contributors

Kari Kirschbaum (author, editor), Animal Diversity Web.

Meredith Kurpinski (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polymorphic

"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

saltatorial

specialized for leaping or bounding locomotion; jumps or hops.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

suburban

living in residential areas on the outskirts of large cities or towns.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

References

Cornell Lab of Ornithology, 1999. "Carolina Wren (Thryothorus Ludovicianus)" (On-line). Accessed March 14, 2001 at http://birds.cornell.edu/birdhouse/speciesaccounts/CAROLINAWREN.htm.

Haggerty, T., E. Morton. 1995. Carolina Wren (Thryothorus ludovicianus). Pp. 1-20 in A Poole, F Gill, eds. The Birds of North America, Vol. 188. Philadelphia, PA: The Academy of Natural Sciences, and Washington, DC: The American Ornithologists' Union.

Hill Collins, Jr., H., N. Boyajian. 1965. Familiar Garden Birds of America. New York: Harper & Row, Publishers, Inc.

Sauer, J. 1997. "USGS: Science For a Changing World, Patuxent Bird Population Studies - Carolina Wren" (On-line). Accessed March 14, 2001 at http://www.mbr-pwrc.usgs.gov/id/framlst/i7180id.html.

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