Song repertoires are often important determining
factors in sexual selection. In several species, older
males have larger repertoires than 1-year-old males. The
development of large song repertoires by an individual is,
however, poorly understood. We studied song element
repertoire changes in five individual male Whitethroats
Sylvia communis sampled as 1- and 2-year olds. These
males increased the size of their element repertoire
between their first and second year, but song length and
number of different elements per song did not change. On
average, 44.3% of the song elements in the first-year repertoire
were also found in the second-year repertoire.
Elements shared between years were found earlier in the
songs and tended to occur in sequences. Sequences of
shared elements also seemed to be conserved between
years. The study suggests that the song element repertoire
of the second year is partly based on the first-year repertoire,
which may explain why large song repertoires are
mainly expressed by males at least 2 years of age. It would
appear, therefore, that song element repertoire size could
be a reliable signal of male age.