Neighbouring territorial songbirds often interact through countersinging,
where birds sing in response to the singing of neighbours such that their
song bouts are temporally related. Complex forms of countersinging
such as song type matching or song overlapping appear to be correlated
with aggressiveness and readiness to escalate confrontations. Less
attention has been paid to the importance of simpler forms of
countersinging, where matched song types are not used and where individual
songs do not temporally overlap.
I examined countersinging behaviour in male Carolina wrens, Thryothorus
which countersing regularly. Why they countersing and
how countersinging is perceived by neighbours is unknown. By
comparing singing behaviour before and after simulated intrusions, I
determined that subjects countersing with their neighbours more readily
when highly aroused.
Comparing responses to countersinging and noncountersinging playbacks
showed that countersinging elicited more aggressive responses than did
noncountersinging. Carolina wrens appear to exchange aggressive
signals regularly through countersinging.