The Carolina wren (Thryothorus ludovicianus) is a common species of wren that is a resident in the eastern half of the United States of America, the extreme south of Ontario, Canada, and the extreme northeast of Mexico. Severe winters restrict the northern limits of their range while favorable weather conditions lead to a northward extension of their breeding range. Their preferred habitat is in dense cover in forest, farm edges and suburban areas. This wren is the state bird of South Carolina.
There are seven recognized subspecies across the range of these wrens and they differ slightly in song and appearance. The birds are generally inconspicuous, avoiding the open for extended periods of time.
Carolina Wren is about 12.5 to 14 cm long, with a 29 cm of wingspan and a weight of about 18 to 23 g. Carolina wren is a fairly large wren; the second largest in the United States species after the cactus wren. Among standard measurements, the wing chord is 5.4 to 6.4 cm; the tail is 4.5 to 5.6 cm. The sexual dimorphism is slight with males being larger than their mates.
There are several differences among the subspecies. For T. l. ludovicianus, the crown is rich brown that appears more chestnut-colored on its rump and uppertail-coverts. Shoulders and greater coverts are a rich brown, with a series of small white dots on the lesser primary coverts. The secondary coverts are rich brown with a darker brown barring on both webs; the bars on the primaries are on the outerwebs only, but darker and more noticeable. The rectrices are brown with 18 to 20 bars that span across the tail.
The white supercilious streak borders thinly with a black above and below, and extends above and beyond its shoulders. The ear coverts are speckled gray and grayish-black. Its chin and throat are grey that becomes buff on its chest, flank and belly, though the latter two are of a warmer color.
The underwing coverts sport a grayish buff color. Its iris is reddish-brown, the upper mandible is lemon-colored and paler at the base and lower mandible. The legs are flesh-colored. Survival rates differ by region, as roughly 90 percent of the Carolina wrens died within 10 years. The easiest species to confuse with the Carolina wren is Bewick's wren, which differs in being smaller but with a longer tail, grayer-brown above and whiter below.
The Carolina and white-browed wrens differ from the house wren in being larger, with a decidedly longer bill and hind toe; their culmen has a notch behind the tip. Carolina wrens adapt to various habitats. Natural habitats include various types of woodland such as oak hardwoods and mixed oak-pine woodlands, ash and elm woods, hickory-oak woodlands with a healthy amount of tangled undergrowth. The preferred habitats are riparian forest, brushy edges, swamps, overgrown farmland, and suburban yards with abundant thick shrubs and trees, and parks.
Carolina wrens sing year round and at any point during the daytime, with the exception of performing during the most harsh weather conditions. Males alone sing, and have a repertoire of at least twenty different phrase patterns and on average, thirty two. One of these patterns is repeated for several minutes, and although the male's song can be repeated up to twelve times, the general number of songs range from three to five times in repetition.
While singing, the tail of the birds is pointed downward. Some general vocalizations have been transcribed as teakettle-teakettle-teakettle and cheery-cheery-cheery. Various descriptions of the teakettle song include whee-udel, whee-udel, whee-udel, che-wortel, che-wortel and túrtee-túrtee-túrtee and familiar names and phrases such as sweet heart, sweet heart, come to me, come to me, sweet William, and Richelieu, Richelieu. Males are capable of increasing their repertoire through song learning, but due to their sedentary nature and territorial defense habits, the song learning must occur within the first three months of life. Their songs can be confused with the Kentucky warbler.
The song patterns are similar, but the warbler's songs are described as richer, with more ringing and a hurried pace. Carolina wrens spend the majority of their time on or near the ground searching for food, or in tangles of vegetation and vines. They also probe bark crevices on lower tree levels, or pick up leaf-litter in order to search for prey. Their diet consists of invertebrates, such as beetles, true bugs, grasshoppers, katydids, spiders, ants, bees, and wasps. Small lizards and tree frogs also make up the carnivorous portion of their diet.
Vegetable matter, such as fruit pulp and various seeds, makes up a small percentage of their diet. In the northern portion of their range, they frequent bird feeders. Carolina wrens are both genetically and socially monogamous and will usually mate for life. Mate changing is rare,[15] and there has been one possible observation of polygamy. During the winter season, males are more responsible for guarding the territory. Females vary in succeeding to maintain winter territories without a mate.