Oxytocin variation and brain region-specific gene expression in a domesticated avian species.

The Bengalese finch was domesticated more than 250 years ago from the wild white-rumped munia (WRM). Similar to other domesticated species, Bengalese finches show a reduced fear response and have lower corticosterone levels, compared to WRMs. Bengalese finches and munias also have different song types. Since oxytocin (OT) has been found to be involved in stress coping and auditory processing, we tested whether the OT sequence and brain expression pattern and content differ in wild munias and domesticated Bengalese finches. We sequenced the OT from 10 wild munias and 11 Bengalese finches and identified intra-strain variability in both the untranslated and protein-coding regions of the sequence, with all the latter giving rise to synonymous mutations. Several of these changes fall in specific transcription factor-binding sites, and show either a conserved or a relaxed evolutionary trend in the avian lineage, and in vertebrates in general. Although in situ hybridization in several hypothalamic nuclei did not reveal significant differences in the number of cells expressing OT between the two strains, real-time quantitative PCR showed a significantly higher OT mRNA expression in the cerebrum of the Bengalese finches relative to munias, but a significantly lower expression in their diencephalon. Our study thus points to a brain region-specific pattern of neurochemical expression in domesticated and wild avian strains, which could be linked to domestication and the behavioral changes associated with it.

Trill-calls in Java sparrows: Repetition rate determines the category of acoustically similar calls in different behavioral contexts.

Bird vocalizations are often differentiated using terms such as "song" and "call." The Java sparrow (Lonchura oryzivora) uses several calls in different behavioral situations; notably, they produce similar calls in disparate situations of aggressiveness or affinity. These calls are composed of short syllables with narrow intervals repeated in quick succession. We distinguished these "trill-calls" as either aggressive or affiliative trills based on behavioral context. We compared the sound pressure levels, frequency of maximum amplitude, entropy, and repetition rate of the two types of trills. Sound pressure level and entropy were higher and trill rate was faster in aggressive trills than in affiliative trills. As these two similarly composed but distinct trill-calls are used in disparate interactive contexts, they could serve as a model system to study the relationship between communicative behavior and brain activity.