The Carolina wren (Thryothorus ludovicianus) is a species of wren common in the eastern United States, the extreme south of Ontario, Canada, the northeast and southeast of Mexico, and into northern Central America. 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.
Ten subspecies are recognized, occurring across the range of the species; they differ slightly in song and appearance. It is generally inconspicuous, avoiding the open for extended periods of time. When out in the open, they energetically investigate their surroundings and are rarely stationary. After finding a mate, pairs maintain a territory and stay together for several years. Both males and females give out alarm calls, but only males sing to advertise territory. Carolina wrens raise multiple broods during the summer breeding season but can fall victim to brood parasitism by brown-headed cowbirds, among other species.
Taxonomy The Carolina wren was first described under the name of Sylvia ludoviciana by John Latham in 1790. Louis Pierre Vieillot at first considered all wrens under the genus Troglodytes and called the Carolina wren Troglodytes arundinaceus, but subsequently placed it in a separate genus Thryothorus (initially misspelled Thriothorus) that he created in 1816.
Etymology The genus name Thryothorus is of Greek origin from the combination of the noun θρύον : thrýon ("rush, reed") and the adjective θοῦρος : thoũros ("rushing, impetuous"; derivative of verb θρῴσκειν : thrōskein to leap up, spring, jump at). Thus, Thryothorus means 'reed jumper'.
Its specific name ludovicianus is a post-classical Latin term for Ludovicus (derivative from Louis XIV) meaning 'of Louisiana' that identifies the locality of the specimen collected near New Orleans.
Species Thryothorus used to be considered the largest genus in the family Troglodytidae, with 27 species, but molecular phylogenetic studies revealed that it represented a polyphyletic assemblage of at least four independent clades now recognized at generic level, with the other 26 species split off in the genera Cantorchilus, Pheugopedius, and Thryophilus. The Carolina wren is now the only species within this genus; DNA work suggests it is most closely allied to Bewick's wren Thryomanes bewickii.
Subspecies Ten subspecies of the Carolina wren are currently recognized:
T. l. ludovicianus (Latham, 1790) – southeast Canada (southern Ontario, irregularly in eastern and southern Quebec) and the eastern United States (southern Wisconsin and New England southward to Texas and northern Florida) T. l. miamensis (Ridgway, 1875) – "Florida wren"; Florida peninsula from approximately 30°N (Gainesville) region southward through the rest of the state T. l. nesophilus (Stevenson, 1973) – "Dog Island wren"; Dog Island in northwestern Florida T. l. burleighi (Lowery, 1940) – "Burleigh's Carolina wren"; islands off of the Mississippi coast, on Cat Island, Ship Island, and Horn Island T. l. lomitensis (Sennett, 1890) – "Lomita wren"; southern Texas (lower Rio Grande Valley) to the extreme northeast of Mexico (Tamaulipas) T. l. oberholseri Lowery, 1940 – southwestern Texas (south-central USA) and northern Mexico T. l. berlandieri (S. F. Baird, 1858) – "Berlandier's wren"; tropical northeastern Mexico (eastern Coahuila, Nuevo León, and southwestern Tamaulipas) T. l. tropicalis Lowery & Newman, 1949 – northeastern Mexico (eastern San Luis Potosí and southern Tamaulipas) T. l. albinucha (Cabot, 1847) – southeastern Mexico (Yucatán Peninsula) to northern Guatemala (Petén) T. l. subfulvus Miller & Griscom, 1925 – arid interior of Guatemala to northwestern Nicaragua
The last two subspecies above, forming a disjunct population in the Yucatán Peninsula of Mexico, Belize, Nicaragua, and in Guatemala, are sometimes treated as a separate species, either known as Cabot's wren or white-browed wren (Thryothorus albinucha). They are included in T. ludovicianus by most authors, however.
Relationships of the Carolina wren to selected other wrens:
Description
At long, with a wingspan and a weight of about , the 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 , the tail is , the culmen is and the tarsus is . Sexual dimorphism is slight with males being larger than their mates. A study indicated that of 42 mated pairs, every male but one was larger than the female of the pair. The males were on average 11 percent heavier along with having longer wing chords.
For T. l. ludovicianus, the crown is rich brown that appears more chestnut-colored on its rump and upper tail 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 dark gray to pinkish-gray, paler at the base and on the lower mandible. The legs are light pinkish to yellowish-brown color.
Several differences are seen among the subspecies. In contrast to T. l. ludovicianus, T. l. berlandieri is of a slightly smaller build, but possesses a larger bill, the upperparts are duller brown with deeper colored underparts, T. l. lomitensis is of a duller color (than either T. l. ludovicianus or T. l. berlandieri) with its underparts either pale or almost white, T. l. miamensis contains darker rusty chestnut upperparts and deeper colored below. T. l. burleighi is duller and sootier with less distinct tail markings, T. l. mesophilus has paler underparts and a whiter supercilium, and T. l. tropicalis is darker than all races, and contains heavier bars than T. l. berlandieri.
Plumage Juvenile T. l. ludovicianus is similar in appearance to the adult, but the plumage is generally paler; a softer texture, buff-tipped wing coverts, and a paler superciliary streak. In August and September, the partial plumage molt for the post-juvenile wrens is darker in color and affects the contour plumage, wing coverts, tail and develops a whiter superciliary stripe. The post-nuptial molt for adults in the same time period is more pronounced in color than the spring molt, with both sexes similar in appearance.
Life span
Survival rates differ by region. A male captured in Arkansas lived to be at least 6 years and 1 month old, and in Alabama, the oldest female and male captured were six and ten years old, respectively. In a survival probability mark-and-recapture study conducted within the southeastern United States from 1992 to 2003, roughly 90 percent of the banded wrens died within 10 years.
Similar species 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 much more obvious supercilium, a decidedly longer bill and hind toe; and the culmen has a notch behind the tip.
Habitat and distribution
These birds are largely resident, and will only disperse beyond their range after mild winters. Carolina wrens sporadically breed as far north as Maine and Quebec after mild winters. In certain parts of their range, such as most of Iowa, prolonged periods of snow can curtail potential expansion. Permanent breeding locations range from eastern Nebraska, southern Michigan, southeast Ontario and the New England states to Mexican states such as Coahuila, Nuevo León, San Luis Potosí and Tamaulipas and the Gulf Coast of the United States. Local occurrences with infrequent and likely breeding locations include southeast South Dakota, central Kansas, eastern Colorado, western Oklahoma and Texas as far as Maine and New Brunswick. There have been occasional vagrants spotted in Colorado, New Mexico, and Arizona, Wyoming, South Dakota, Manitoba, Nova Scotia, and the Gulf of St. Lawrence.
The range of the wrens increased northward and westward in several regions over the past few centuries. In Massachusetts, the wrens had expanded westward and northeastward from its former southeastern location in approximately 35 years, in New York the population increased three-fold in roughly 25 years, while in the midwest states of Ohio and Michigan, numbers have increased since the mid-1800s and early 1900s, respectively. Expansion around Ontario occurred since early reports in 1890 and 1905. Explanations given include infrequent winter storms in the 20th century, expanded forest habitats, and the wrens taking advantage of urban areas containing feeders, especially in winter. From 1966 to 2015 the Carolina wren experienced a greater than 1.5% annual population increase throughout most of its northern range, extending from southern Maine to southern Nebraska.
Carolina wrens adapt to various habitats. Natural habitats include various types of woodland such as oak hardwoods and mixed oak-pine woodlands, ash and elmwoods, 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. It has an affinity for dilapidated buildings and unkempt yards in man-made areas. Subspecies T. l. burleighi and T. l. neophilus inhabit slash pine and palmettos.
Behavior
Song and calls
Carolina wrens sing year round and at any point during the daytime, except 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 ranges 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. Geographic barriers affect song repertoire size from male wrens, as one study indicated that distances separated as close as by water barriers can have the same effect as that of a distance of in the mainland with no barriers.
Female Carolina wrens possess song control regions that would appear to make them capable of singing with repertoires like the male. Due to vocalizations that they occasionally make with the male, it has been suggested that song perception plays a role and is of behavioral relevance.
Different subspecies have variations in songs and calls, such as miamensis having a more rapid song that contains more notes than the races that are further north.