Behaviour 142, Issue 11
http://www.ingentaconnect.com/content/brill/beh/2005/00000142/f0020011
Sharp, SP & BJ Hatchwell (2005) Individuality in the contact calls of
cooperatively breeding long-tailed tits (Aegithalos caudatus). Behaviour 142:
1559-1575.
The ability to discriminate between individuals or groups of individuals is
important for the evolution of sociality. Individual vocal recognition is
thought to be widespread in social birds, yet few studies have investigated its
role in cooperatively breeding species. In long-tailed tits, helpers
preferentially provide care to close kin, and individuals are able to
discriminate between the vocalisations of kin and non-kin. However, the
mechanism underlying this recognition system is unknown. Here we quantify the
relative variation between and within individuals in three of the contact calls
used by this species. Spectrographic cross-correlation revealed that two of
these calls, the 'churr' and the 'triple', were individually distinct. We
therefore analysed the variation in a series of acoustic parameters in each of
these two vocalisations. For both the churr and the triple, discriminant
function analysis was able to allocate calls to the correct individuals
according to var
iation in several frequency parameters. We hypothesise that long-tailed tits
are able to discriminate between the calls of conspecifics based on these
parameters. This is the first quantitative description of potential recognition
cues in a cooperatively breeding bird in which vocal discrimination is known to
occur.
|