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There are relatively few quantitative descriptive studies of the vocalisations and vocal behaviour of tropical bird species, in spite of the tropic's rich avian biodiversity and the extensive variety of vocalisations produced by tropical birds. This lack of information inhibits our understanding of tropical animals, including our ability to perform comparative analyses on vocal behaviours from an evolutionary perspective. In this study, we present the first quantitative description of the vocal repertoire and daily vocal activity of White-eared Ground-sparrows ( Melozone leucotis), using focal and autonomous recordings collected during two consecutive breeding seasons in Costa Rica. We classified vocalisations into categories based on their visual appearance on sound spectrograms to create a library of vocalisations for this species. We found that White-eared Ground-sparrows produce three main categories of vocalisations: solo songs, calls, and duets. Solo songs were produced only by males. Each male sang a repertoire of solo song types, which all shared the same general structure with short introductory notes, a frequency-modulated middle section, and a terminal trill. Both sexes produce calls and coordinated vocal duets. We quantified patterns of diel variation in each category of vocalisation, and found that the Ground-sparrows produced all three vocalisations at higher output at dawn (between 0500 and 0600 hours) compared to the rest of the day. This study allowed us to conduct the first comparisons of vocalisations between White-eared Ground-sparrows and North American species in the genus Melozone, and revealed both similarities and differences between the species groups. Our investigation also showed that vocalisations related to communication within pairs and to territory defence (calls and duets) exhibited lower levels of individual distinctiveness than vocalisations related mainly to female attraction (male solo songs). Our observations suggest that each of the three types of vocalisations have multiple functions in White-eared Ground-sparrows, revealing diverse communication functions with a small vocal repertoire in this tropical songbird. [ABSTRACT FROM AUTHOR]

During the breeding season, Pied Avocets, Recurvirostra avosetta, produce five morphologically distinct syllables-chuck, chirp, whistle, coo and snarl-which form the basis of the species' adult vocal repertoire. Chuck, chirp and whistle each contribute to several call types distinguished by the temporal arrangement of the syllables that make them up, whereas coo and snarl are monosyllabic calls. Here, I document the ontogeny of these five syllables up to 11 months of age in birds reared from the egg. Sonagraphic analysis, together with the behavioral context in which the calls were uttered, suggests that both chuck and chirp syllables develop gradually from prenatal vocalizations, whereas snarl and coo syllables emerged de novo at 8 and 12 weeks of age, respectively, with the coo developing earlier in males than in females. Interestingly, the captive birds failed to develop the whistle, raising the possibility that social interactions with adults may be necessary for its production. After the breaking of the voice, which occurs at 9 months of age, syllable morphology closely resembled that of adults in the wild. This study enabled me to elaborate a synthetic tree of call development in Pied Avocets, which suggests working hypotheses to account for the unfolding of the species' call repertoire. [ABSTRACT FROM AUTHOR]