Data from: A superb solo, or a deviant duet? Overlapping songs in superb fairy-wrens

Avian duets are formed when two birds coordinate their songs. Most
research on the evolution and function of duetting has focused on species
with highly coordinated duets, and less is known about the context and
function of overlapping songs that are more loosely coordinated, in part
due to the challenge of determining whether such vocalisations coincide by
chance or through coordination between the partners. Here, we use field
recordings and playback experiments to test whether breeding pairs of
superb fairy-wrens Malurus cyaneus, coordinate their territorial songs to
form duets. We test three key characteristics of duetting; whether
partners’ songs 1) overlap more than expected by chance; 2) have a
stereotyped structure that occurs repeatedly and predictably in time, and
3) show evidence of a constant time lag between the contributions of the
two participants, indicating that individuals are coordinating their
songs. This is the first study to quantify the temporal precision of song
between partners to investigate coordination in the Malurus genus, an
important model taxon for song, sexual selection, and speciation. We found
variation in the extent to which partners’ songs overlapped, with some
individuals overlapping their partners’ songs more than expected by
chance, no difference in structure of solo and overlapping songs, and no
evidence of a consistent response interval. Thus song overlap in superb
fairy-wrens meets only some criteria for duetting. We suggest that
overlapping songs in this species may be due to individuals responding
independently to the same stimulus and/or ‘call and answer’ between pair
members.