Abstract:
Individuals of a given population share more behavioural traits with each other than with members
of other populations. For example, in humans, traditions are specific to regions or countries.
These cultural relationships can tell us about the history of the populations, their origin and the
amount of exchange between them. In birds, regional dialects have been described in many
species. However, the mechanisms with which dialects form in populations is not fully understood
because it is difficult to analyse experimentally. Translocated populations, with their
known histories, offer an opportunity to study these mechanisms. From the study of bird vocalisations
we can make inferences regarding population structure and relationships as well as their
history, individual behavioural state, neuronal and physiological mechanisms or development
of neuronal learning. Too achieve this, cross-disciplinary approaches are necessary, combining
field work, bioacoustic methods, statistical tools such as machine learning, ecological knowledge
and phylogenetic methods. Here, I will describe computational methods for the treatment
and classification of bird vocalisations and will use them to depict the relationships between
bird populations. First, I discretise the data in order to define the cultural traits. Then phylogenetic
tree-building methods are used. Two approaches are possible, first to map these traits onto
known phylogenies and, second, to directly build the phylogeny of these traits. I describe the
application of these methods to test several hypothesis on bird songs evolution related to both
their history and the mechanisms with which they evolve. Evidence for the presence of dialects
in the Puget Sound white-crowned sparrow (Zonotrichia leucophrys pugetensis) is provided
on the basis of the syllable content of the songs. The absence of vocal sexual dimorphism is
reported in the Australasian gannet (or takapu, Morus serrator), a member of the Sulidae family
for which extensive sexual dimorphism has been reported in other species. Subsequently,
convergence between the begging calls of several cuckoo species and their respective hosts is
suggested by various bioacoustic methods. In addition, the male calls of the hihi (or stitchbird,
Notiomystis cincta) is analysed in an island population. The corresponding pattern of variation
suggests a post-dispersal acquisition of calls via learning which is in agreement with the most
related species in the revised phylogeny of the hihi. Finally, the mechanisms of song evolution
are depicted in translocated populations of tieke (or saddleback, Philesturnus carunculatus
rufusater), resulting in the development of island dialects.