It is easiest to confuse with the Bewick's Wren, a fairly close relative[2], 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
[edit] Song and calls
The Carolina Wren is noted for its loud song, popularly rendered as "teakettle-teakettle-teakettle". This song is rather atypical among wrens, which tend to sing songs which are similar to other wrens' songs. A given bird will typically sing several different songs. Only the male birds sing their loud song. The songs vary regionally, with birds in northern areas singing more slowly than those in southern areas.
The Carolina Wren also has a series of calls, including a rapid series of descending notes in a similar timbre to its song, functioning as an alarm call, and a very harsh and loud scolding call made to threaten intruders.