Description and Ecology
The Carolina Wren (Thryothorus ludovicianus) is a small (13 cm) songbird in the wren family (Troglodytidae), which is found exclusively in the Americas. Despite it’s small size, the Carolina Wren is the largest wren species commonly found in North America. Other wrens occurring in the Great Lakes Region include the House Wren (Troglodytes aedon), Winter Wren (Troglodytes hiemalis), Marsh Wren (Cistothorus palustris), and Sedge Wren (Cistothorus platensis). Wrens are also closely related to Blue-Grey Gnatcatcher (Polioptila caerulea). The Carolina Wren is widely distributed across eastern North America from southern Ontario to Florida and northeastern Mexico, with a disjunct population in the rainforests of the Yucatan Peninsula.
Unlike many small insectivorous birds in the region, Carolina Wrens are non-migratory, remaining in the same region year-round. Their preferred habitats include dense deciduous forests, oak savannas, swamps, shrublands, riparian areas and urban parks. Staring in February, male Carolina Wrens sing loudly to establish a breeding territory and attract a mate. Their song is described by the mnemonic “teakettle-teakettle-teakettle” or variations of repeated, musical phrases. Male Carolina Wrens sing throughout much of the year, though they are almost silent between November and January. They are especially vocal between the months of March and May, when pairs reaffirm territory and breeding bonds. Carolina Wrens are sexually monogamous – pairing for life, typical for non-migratory songbirds, and larger waterfowl, such as Geese (Branta canadensis) and Trumpeter Swans (Cygnus buccinator).
Each summer, Carolina Wrens typically raise 2–3 broods. Nests are dome-shaped and made in cavities or covered locations. The female lays 4–6 eggs per clutch, which are white to creamy with reddish-brown speckles. She performs most of the incubation, which lasts about 13 days, the young fledge 13 days after hatching. Both parents feed the nestlings.
Carolina Wrens are primarily insectivorous, consuming a wide variety of small invertebrates including beetles (Coleoptera), caterpillars and moths (Lepidoptera), grasshoppers and crickets (Orthoptera), spiders (Araneae), ants and wasps (Hymenoptera), and true bugs (Hemiptera). In autumn and winter, when insects are scarce, Carolina Wrens supplement their diet with berries and seeds, including cherries (Prunus sp.), serviceberries (Amelanchier sp.), hawberries (Crataegus sp.), grapes (Vitis sp.), spicebush berries (Lindera sp.), snowberries (Symphoricarpos sp.), sumac (Rhus sp.), bayberry (Morella sp.), elderberry (Sambucus sp.), and many other fruits. They often visit feeders to consume suet and sunflower seeds from feeders. Their adaptability in winter feeding is one of the key factors in their range expansion northward.
The Carolina Wren population is large in North America, estimated at around 20 million breeding birds. In recent years, Carolina Wren populations have been expanding northwards, in part due to human settlement, which often results in large amounts of edible material for the species in the colder months. Warm winters (often resultant of a strong El Nino in the Pacific Ocean) result in population expansions. Between these years, the more common, characteristic harsh winters of the Great Lakes sometimes reduce numbers, but populations tend to rebound quickly due to high reproductive output and adaptability to human-altered environments.
Written by Matthew Palarchio, HBSc in Environmental Sciences, Western University
All photos are Stock photos retrieved from Canva
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