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Thryomanes bewickiiBewick's wren

By Sarah King

Geographic Range

Bewick’s wrens (Thryomanes bewickii) are typically not a migratory species and mainly stay in the same habitat year-round. However, some travel to higher elevations for protection and leave northern climates to find warmer areas during winter. Bewick’s wrens typically reside in the northern United States. They are native to North America and are most abundant on the Pacific Coast, from Baja California to Washington. They are also found in parts of the southwestern states such as Arizona, New Mexico, and Texas. Bewick’s wrens used to inhabit parts of the east coast, but have recently been extirpated from these areas due to climate change and other environmental factors. They can also be found in Mexico, as they flourish in warmer climates. (Kennedy and White, 2013; Verner and Purcell, 1999)

Habitat

Bewick’s wrens prefer chaparral-type environments as well as sage scrub. They are often found in dry, bushy climates but also in woody areas near running water. Bewick’s wrens find protection in cavities such as caves, rocks, and holes. They mainly nest in the cavities of trees including live oaks and willows. Frequently, they will create nests in manmade structures such as wood buildings and birdhouses. The overabundance of manmade structures and urbanization have not caused a significant shortage of wren population size. (Miller, 1941; Robert, 2003; Unitt, 2004)

Physical Description

Bewick’s wrens are relatively small birds, measuring about 14 cm long and weighing about 10 g. They have a round body shape and brown backs with greyish-white bellies. They are mainly distinguished by a white strip that runs right above their eyes, giving them the appearance of having eyebrows. Their tails are long and striped with brown and white. They flick their tails as they hop from branch to branch and often hold their tails up high. They have sharp, slightly curved beaks that they use to crack seeds and capture small invertebrate prey. Their feet are clawed to grip food and provide balance. Male and female Bewick’s wrens do not have any distinguishable differences. Juveniles are slightly paler than adults, but generally have the same features. Exact coloring varies in different regions. Bewick’s wrens that live further north have rustier plumage color than those that live farther south. (Kennedy and White, 2013; Unitt, 2004)

  • Sexual Dimorphism
  • sexes alike
  • Average mass
    10 g
    0.35 oz
  • Average length
    14 cm
    5.51 in
  • Average wingspan
    18 cm
    7.09 in

Reproduction

Bewick’s wrens are seasonal breeders and engage in monogamous relationships beginning every spring. During winter, they are mostly solitary. When the next breeding season approaches, Bewick's wrens look for new mates. They reach sexual maturity and begin breeding at around one year old. Both males and females make short, high-pitched calls; however, males are the only ones that have a specific song to attract mates. An individual male can possess anywhere from 9 to 22 different songs. These songs may be different depending on what geographic area that specific bird lives in. Songs consist of combinations of whistles and trills. Females choose mates based on vocal range and singing ability. The males will stop their song when they hear other competitors singing to chase them down. This increases their chances of having the female pick them. (Kennedy and White, 2013; Pearse, et al., 2004; Smith, 2016)

Once female Bewick's wrens pick mates, they will form pairs and the males will begin building a nest. Nest building takes 1 to 8 days, depending on the arrival time of the eggs. Nests are composed of twigs, woody material, and feathers. Males and females typically pair up in the springtime and stay paired until winter. Once nests are built, pairs reproduce. Bewick’s wrens are oviparous, with females lay 3 to 8 white eggs that are oval-shaped and spotted brown. Pairs produce one or two broods within the breeding season that are roughly 43 days apart. It is possible, though uncommon, for these pairs to produce a third brood. They will move locations and refrain from laying both broods in the same spot twice. Typically, females lay one egg per day until the entire brood had been laid. The spotting on eggs ranges in color and pigmentation, some being redder and some browner. The first eggs of broods are typically the smallest, and the last eggs are the largest.

Females sit tightly on their eggs until they hatch, which takes about 15 days after the last eggs are released. Females remove any eggshells stuck on their offspring. Baby chicks have tufts of fluffy feathers, yellow beaks, and pink skin. Both mothers and fathers show extensive parental care. Males scavenge for food for the chicks while females remain with chicks and remove the fecal sacs they produce. At around the 12th day after hatching, chicks are fully covered with feathers. Juveniles are able to fly after roughly 17 days. Mothers and fathers continue to nurture their offspring for about two weeks after they are fledged, at which point they are capable of living on their own.

  • Average eggs per season
    3-8
  • Average time to hatching
    14-16 days
  • Average fledging age
    17 days
  • Average time to independence
    2 weeks
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Female Bewick's wrens sit tightly on their eggs until they hatch, which takes about 15 days after the last eggs are released. Females remove any eggshells stuck on their offspring. Baby chicks have tufts of fluffy feathers, yellow beaks, and pink skin. Both mothers and fathers show extensive parental care. Males scavenge for food for the chicks while females remain with chicks and remove the fecal sacs they produce. At around the 12th day after hatching, chicks are fully covered with feathers. Juveniles are able to fly after roughly 17 days. Mothers and fathers continue to nurture their offspring for about two weeks after they are fledged, at which point they are capable of living on their own.

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

Lifespan/Longevity

The longest-lived Bewick’s wren recorded in the wild lived 8 years. In captivity, Bewick's wrens can live much longer due to the lack of predation. Most wrens do not live to be 8 years old due to environmental threats. They tend to live to be about 5 or 6 years old. (Lutmerding and Love, 2019)

  • Average lifespan
    Status: wild
    8 years
  • Average lifespan
    Status: wild
    5-6 years

Behavior

Bewick’s wrens are diurnal and do not migrate far. During the breeding season, several calls and songs can be heard to defend territory and to find mates. Bewick’s wrens are very loud and hyperactive. They display several different body positions depending on the songs or calls they are producing. When Bewick's wrens want to show authority or warn predators, they will stick their tails up high and make vocal calls with different frequencies. They are often seen wagging their tails back and forth and fanning their feathers to show territorial defense. When male Bewick's wrens want to court females, they will hold their heads high and tuck their tails under their bodies.

Bewick’s wrens can hang upside down to catch their invertebrate prey. They are often seen on the ground hopping around and picking for insects. Often, Bewick's wrens will strike their prey against hard surfaces to kill them before ingestion. After they kill their prey, Bewick's wrens swallow the entire insect whole as they do not posses any teeth. They can be seen wiping their bills on nearby plant material to clean off insect residue. With a wingspan of about 18 cm, Bewick’s wrens can only fly for short periods of time. They tend to glide through the air and have weak fluttering ability. They have rounded wings and shallow wing beats during flight. Other than flight, Bewick's wrens mostly move by hopping along the ground. (Kennedy and White, 2013; Peterson, 1980; Waite, 2013)

Communication and Perception

Bewick’s wrens primarily communicate with their own species. One of the only exceptions is communicating with predators to warn them away. Bewick's wren males begin developing their songs as they establish a new territory. They will learn different frequencies and cues from neighboring wrens that are also establishing territory. Males do not develop their songs from a paternal vocal array. Female Bewick's wrens are vocal, but they do not build as complex a vocal repertoire as males do. Males begin developing their songs by copying their local neighbors. They often make mistakes in copying, leading to their own unique sound. It has been observed that offspring typically do not develop a song until after migration to a sustainable territory.

Bewick’s wrens do not acquire vocal techniques from any species other than their own. The typical song includes 3 to 5 phrases with 1 to 2 distinct trills. Populations in close geographic proximity can have similar songs, since they learn from each other. Bewick's wrens in the eastern portion of the range tend to acquire a 5-phrase song that is similar to "see-teu-whee-teu-eee". This sound is like the vocals of song sparrow (Melospiza melodia). Offspring will give calls to their parents indicating they need food or indicating they need directional help after fledging. This sound is not a song but rather a short burst sounding like "sc-i-i-t". Females will give out short sounds like "sker" and "swee" when attempting to get the attention of nearby birds. They give out the same "sc-i-i-t" sound as offspring when they are waiting for their mate to bring food. Other than vocal sounds, Bewick’s wrens occasionally snap their beaks to show aggression and warn predators. Male Bewick's wrens hold their heads high to give females a visual cue that they are looking for a mate. Bewick’s wrenss do not exhibit any tactile or chemical cues for communication purposes. They tend to not sing as a group, being that they have their own individualized song.

Bewick’s Wrens are very aware of their surroundings. They have color cones in their eyes that allow them to see a wide range of colors that humans cannot see. Their eyes are very sensitive to ultraviolet rays with these additional cones. They have good vision, which allows them to spot predators quickly. They are endothermic and do not need environmental heat to regulate their own body temperatures. Although they are endothermic, they are also facultative sunbathers. Bewick’s Wrens have highly developed hearing, allowing them to detect very high and low-pitched sounds. (Fleischer, et al., 1985; Kennedy and White, 2013; Smith, 2016)

Food Habits

The main food source for Bewick’s wrens is arthropod adults and larvae. They are ground foragers and use their pointed beaks to extract arthropods from bushes or shrubs. In some western regions, females forage on the ground while males forage higher in the trees. This allows for a wider range of food options and a better chance of finding food. Bewick's wrens prefer live food and will kill them upon ingestion. They will kill the insect either by shaking or smashing it. Typically, they will swallow their prey whole but sometimes remove the extremities first. Bewick's wrens peck for their food. The three main locations of foraging include in live oak, in buckbrush, and on the ground. Bewick's wrens feast on bugs (order Hemiptera), beetles (order Coleoptera), bees (order Hymenoptera), caterpillars and butterflies (order Lepidoptera), and some vegetation. They are mainly insectivorous, but eat materials such as fruit pulp and seeds as well. Bewick’s wrens tend to find more live prey during the summer, when the weather is warmer. They eat the highest amount of plant matter during the winter season, when insects are less abundant. As they forage, they may ingest some mud and dirt, though this provides little nutrition. (Kennedy and White, 2013; Kyle, 1987)

  • Animal Foods
  • insects
  • Plant Foods
  • wood, bark, or stems

Predation

Bewick’s wrens are most susceptible to predators in the early stages of life, though the list of potential predators changes slightly in adults. Snakes (suborder Serpentes) are the biggest threat to eggs and juveniles. Some snake predators include black rat snakes (Pantherophis obsoletus), Great Plains rat snakes (Pantherophis emoryi), and eastern milk snakes (Lampropeltis triangulum). Domestic cats often feed on Bewick’s wren eggs as well as juveniles. Sharp-shinned hawks (Accipiter atriatus) are common predators of adults. Hawks are one of the main predators for adult Bewick’s wrens as they can sneak up on them very efficiently. Roadrunners (genus Geococcyx) and rattlesnakes (genus Crotalus) often eat Bewick’s wrens when they are on the ground.

Though they are not predators, house wrens (Troglodytes aedon) are common competitors with Bewick’s Wrens. Occasionally, house wrens will steal the eggs of Bewick's wrens. This is a territorial act and infers that the House Wrens are superior and more powerful. (Hendricks, 1995; Kennedy and White, 2013)

Ecosystem Roles

Bewick’s wrens control the populations of the insects on which they feed. In this way, they contribute to stable insect communities and local habitat health. Predators such as hawks who eat Bewick’s wren would be without an important food source as well. Bewick's wrens do not carry any known diseases nor are they host to any parasite species. (Kennedy and White, 2013)

Economic Importance for Humans: Positive

There is no significant evidence that Bewick’s Wrens provide an economic benefits to humans. However, they are a popular birdwatching species.

  • Positive Impacts
  • research and education

Economic Importance for Humans: Negative

There are no known negative impacts of Bewick’s wrens on humans.

Conservation Status

The IUCN Red List has listed Bewick’s wrens as a species of least concern. There has been no obvious rise or decline in their populations, and they are exhibiting stable population trends. No conservation actions are being made to protect this species directly. There is however a monitoring system across the globe to keep track of the populations ensuring no population declines are taking place. The US Migratory Bird Act has listed Bewick’s wrens as a protected species. There is no significant status on the US Federal List and the Convention on International Trade in Endangered Species (CITES) has no special status for Bewick’s wrens.

As they do not have established populations in Michigan, the State of Michigan List also listed the Bewick’s Wren as having no special status. The only two known causes of Bewick's wren population declines are human-related or due to competition. Destruction of habitat due to industrialization as well as a low supply of nest boxes has been noted to cause some declines. House wrens (Troglodytes aedon) are notorious for destroying Bewick’s wrens nests, but there is no need for extensive conservation efforts to protect against mortality from this factor. Western regions are experiencing some level of decline due to the loss of nesting sites. (BirdLife, 2018; Kennedy and White, 2013)

Other Comments

English naturalist Thomas Bewick was the friend of the famous bird artist, John James Audubon. Audubon studied birds extensively and named Bewick’s wrens after his very close friend. (Kennedy and White, 2013)

Contributors

Sarah King (author), California State University, San Marcos, Tracey Brown (editor), California State University, San Marcos, Galen Burrell (editor), Special Projects.

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

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

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.

arboreal

Referring to an animal that lives in trees; tree-climbing.

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

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

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.

saltatorial

specialized for leaping or bounding locomotion; jumps or hops.

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

solitary

lives alone

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

suburban

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

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.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

References

BirdLife, I. 2018. "Bewick's Wren" (On-line). IUCN Red List. Accessed April 27, 2020 at https://www.iucnredlist.org/species/22711377/132096463.

Fleischer, R., W. Boarman, M. Cody. 1985. Asynchrony of song series in the Bewick's Wren and Wrentit. Animal Behaviour, 33: 674-676.

Hendricks, P. 1995. Bewick's and House Wrens at a common dusting site, with comments on the utility of dusting. Journal of Field Ornithology, 66: 492-496.

Kennedy, E., D. White. 2013. Bewick's Wren (Thryomanes bewickii). Pp. 1-50 in A Poole, ed. Birds of North America, Vol. (2). New York: Cornell Lab of Ornithology. Accessed February 29, 2020 at https://birdsna.org/Species-Account/bna/species/bewwre/introduction.

Kyle, P. 1987. Hand-rearing Carolina and Bewick's Wrens. Wildlife Journal, 10: 4-8.

Lutmerding, J., A. Love. 2019. Longevity records of North American birds. USGS, 1019: 1-1. Accessed April 01, 2020 at https://www.pwrc.usgs.gov/BBL/longevity/Longevity_main.cfm.

Miller, E. 1941. Behavior of the Bewick Wren. Oxford Journals, 43(2): 81-99. Accessed March 10, 2020 at https://www.jstor.org/stable/pdf/1364411.pdf?casa_token=s0_cknoB8rUAAAAA:9c-CTh6FEiiNoNonPTvMaj1Lsa9X0tj5wudi1hOhe-SVyjRgJvUlhtCGeDkBLFsqEQ1acA-vO0Tk5pOI3b7Ts3t6WOi7C4ZBFb2uz2-F4rqa1c8bLg.

Pearse, A., J. Cavitt, J. Cully, JR. 2004. Effects of food supplementation on female nest attentiveness and incubation mate feeding in two sympatric wren species. BioOne Complete, 116(1): 23-30. Accessed March 20, 2020 at https://doi.org/10.1676/0043- 5643(2004)116[0023:EOFSOF]2.0.CO;2.

Peterson, R. 1980. A Field Guide to Western Birds. National Wildlife Federation: Peterson Field Guides.

Robert, T. 2003. Factors influencing expansion of the breeding distribution of Bewick's Wren into riparian forests of the Rio Grande in Central New Mexico. BioOne Complete, 48(3): 373-382. Accessed March 10, 2020 at file:///C:/Users/king1/Downloads/0038-4909_2003_048_0373_FIEOTB_2.0.CO_2.pdf.

Smith, E. 2016. Bewick's Wren (Thryomanes bewickii). Sialis, 1(1): 81-99. Accessed April 01, 2020 at http://www.sialis.org/bewrbio.htm.

Unitt, P. 2004. The San Diego County Bird Atlas. San Diego County: University of California Press. Accessed February 29, 2020 at http://sdplantatlas.org/birdatlas/pdf/Bewick's%20Wren.pdf.

Verner, J., K. Purcell. 1999. Fluctuating populations of the house wrens and bewick's wrens in foothills of the Western Sierra Nevada of California. Oxford Journals, 101(2): 219-229. Accessed March 10, 2020 at https://www.jstor.org/stable/pdf/1369985.pdf?casa_token=OJU0k-n5qn8AAAAA:ocyOF9RazmxK2LfUm1eznp1VoySZ1v2jYV5OJMK3FATTvKtEAOSWSbPP-qurTGfj76M0_zRIJ2oPPBGQI3KMAH2gACKx0K5wBiayxj2x7lpqwtLgZw.

Waite, M. 2013. "Field Guide to Birds of North America" (On-line). What Bird. Accessed April 01, 2020 at https://identify.whatbird.com/obj/135/identification/Bewicks_Wren.aspx.

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