IUCN threat status:

Least Concern (LC)

Comprehensive Description

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Bewick’s wren (Thryomanes bewickii), is a common North American perching bird in the order Passeriformes and the family Troglodytidae.  This species is native to Canada, Mexico, and the United States and is located mainly from southwest British Columbia through the western and south-central United States, and deep into central Mexico, with rare appearances in the eastern United States (Birdlife International 2016).  Due to its large geographic range, it can be found in diverse habitats such as thickets, underbrush, gardens, streamside groves, rivers, chaparral-covered hillsides, desert washes, and suburban areas (Kaufmann 2018).

This small bird has a distinctive bold white line that extends over the eye to the back of the neck and also has white spots on the tail.  It features a slender body with a long tail, grey or whitish belly, and brown to greyish brown back.  The average length is 13 cm, but males are slightly larger than females, with a wing length of 58.2 mm and 55.6 mm respectively.  It has an average weight of 10-11 g, which is similar to other North American wrens (Kennedy and White 2013).

Bewick’s wrens are highly active, often hopping about in the trees within 10 feet of the ground, or beelining to their next destination when they leave their vegetative cover. They forage both by probing tree bark and searching through leaf litter on the ground. Their diet consists mainly of small invertebrates, namely grasshoppers, beetles, wasps, spiders, bugs, moths, and caterpillars, but also includes seeds and fruit. When they catch their prey, they crush it or shake it to death before swallowing it whole. They are usually solitary foragers until mating season, but some pair bonds persist throughout the year, possibly to prevent the partner from mating with another bird. Though many stay in one place all year, some migrate from northern areas and higher elevations in winter. Those that inhabit eastern regions may be more prone to migration than those from the west (All About Birds 2018; Kaufmann 2018; Seattle Audubon 2018).

Mating songs of T. bewickii are done by males only. The melodious territorial song consists of 3-5 phrases with 1-2 trills, performed with a markedly vigorous rhythm. Clutches are started over a long period, beginning in mid-March in Oklahoma and early April in Kansas and Oregon. Females lay 1 egg per day until the clutch is complete, which typically consists of 5-7 eggs, but sometimes as many as 11. The young hatch about 14 days after the laying of the penultimate egg, and the earliest hatching dates are late March/early April in southern populations and late April/early May in northern populations (Kennedy and White 2013). The oldest recorded Bewick’s wren was at least 8 years old when it was recaptured and released in 1986 (All About Birds 2016).

Predators of the Bewick’s wren include the black rat snake, Great Plains rat snake, and eastern milk snake, which prey on the eggs and nestlings, while sharp-shinned hawks, greater roadrunners, and rattlesnakes prey on adults.  There is also much competition between other species of wrens and some will remove eggs or kill nestlings.  With few predators and an extremely large and stable population this species is considered of least concern by the IUCN (Bird Life International 2016).  However, some populations within the United States are at a risk, particularly in the eastern United States, where they have mostly disappeared, possibly due to the expansion of house wrens and other competitors (Kennedy and White 2013; Seattle Audubon 2018).

Unreviewed

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© Rylan Anderson, Brianna Bonam, Benjamin Dirks, Editor: Dr. Gordon Miller

Supplier: seattleu_natural_history

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