Vocal behaviour of White-eared Ground-sparrows (Melozone leucotis) during the breeding season: repertoires, diel variation, behavioural contexts, and individual distinctiveness

Abstract

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 Groundsparrows 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. ZusammenfassungGesangsverhalten von Weißohrammern (Melozone leucotis) während der Brutzeit: Repertoires, Tagesvariation, Verhaltenskontext und individuelle Charakteristik Trotz des Vogelartenreichtums der Tropen und der großen Vielfalt an Lautäußerungen tropischer Vögel, gibt es verhältnismäßig wenige quantitativ-beschreibende Studien zu Vokalisation und Gesangsverhalten tropischer Vogelarten. Dieser Mangel an Informationen vermindert unser Verständnis tropischer Vögel, einschließlich der Fähigkeit, vergleichende Analysen zum Gesangsverhalten aus Sicht der Evolution durchzuführen. In dieser Studie präsentieren wir Communicated by C. G. Guglielmo. Electronic supplementary materialThe online version of this article (

Dual Function of Chip Calls Depending on Changing Call Rate Related to Risk Level in Territorial Pairs of White‐Eared Ground‐Sparrows

“…These values of rates corresponded with the range of natural variation in rates of delivery for these calls based on our observations of wild birds (Sandoval et al. ).…”

“…Based on previous field observations, where White‐eared Ground‐sparrows produced chip calls at higher rates when a predator was close to chicks and nest (Sandoval et al. ), this suggests higher call rate provides information on the level of risk to the receivers. Similar, Black‐capped and Carolina Chickadee ( P. carolinensis ) under higher levels of risk, that is, closer predators or predator faster approaching, moved faster to the stimulus to assess the type of predator and adjust antipredatory behaviors according to the level of risk (Templeton et al.…”

“…White‐eared Ground‐sparrows produce two types of calls ( tseet and chip ), which vary in duration and bandwidth (Sandoval et al. ). Whereas tseet call is used mainly as a contact signal between both members of the pair, chip call has been observed to be used as a contact signal (e.g., during foraging along their territories) and as alarm signals when a predator is near the nest or fledglings (e.g., included pygmy owls, dogs, and snakes; birds behaved similarly when humans were close to the nest) (Sandoval et al.…”

“…Therefore, we have observed that under both contexts, chip call rates vary, and it is possible that these different call rates represent distinct meanings (Sandoval et al. ).…”

A song for the South also: defining birdsong in global terms

“…White‐eared Ground Sparrow Melozone leucotis , Sandoval et al . ) or in coordinated duets (e.g. review by Hall ). These vocalizations may be strongly seasonal in occurrence (e.g.…”