Data from: Rock wrens preferentially use song types that improve long distance signal transmission during natural singing bouts

When animals are capable of producing variable signals they may
preferentially use some signal types over others. Among songbirds,
individuals are known to alter song type form and usage patterns in
contest and mating situations, but studies have not examined how song
choice improves signal efficacy during broadcast song. For this study we
investigated rock wren Salpinctes obsoletus song type use rates during
natural singing bouts. We tested three hypotheses for adaptive song use
during broadcast song: 1) birds improve signal content by increasing the
use of high quality songs, 2) birds optimize for signal propagation by
preferentially using songs that transmit well, and 3) birds maintain
energy by reducing the use of costly songs. The study included 19 058
songs sung by 12 individuals, each of which had a measured song repertoire
of between 52 and 117 song types which were produced at highly variable
rates. Results indicated that rock wrens did not preferentially sing song
types with shorter durations or fewer frequency switches, as would be
expected if they selected song types to minimize delivery costs. They also
did not favor songs with more rapid trills or more frequency switches, as
would be expected if they adjusted song use primarily to indicate quality.
Focal birds did preferentially sing significantly longer songs with lower
bandwidths, lower frequencies, and slower trill rates. Results suggest
that natural broadcast singing patterns are shaped more by the benefits of
long distance transmission than by the benefits of advertising performance
ability or the costs of song production.