Vocal behaviour of Sclater’s Wrens, a duetting Neotropical songbird: repertoires, dawn chorus variation, and song sharing

Diverse evolutionary forces have promoted the great diversity of vocal behaviour found in birds. The description of such behaviour is crucial for understanding both selective and non-selective pressures shaping acoustic signals in birds and their role in ecological and evolutionary processes. Here, we describe the vocal behaviour of the Sclater’s Wren (Campylorhynchus rufinucha humilis), a songbird species that lives in Neotropical dry forests. Using active and passive acoustic monitoring, we quantified sex-specific solo song repertoires, described the acoustic structural characteristics of the songs, assessed vocal activity during the dawn chorus including calls, solo songs, duets and sex contribution to duet formation, and tested whether the degree of song sharing varied with geographical distance between neighbouring territories. Our results based on 24 pairs suggest that Sclater’s Wrens have sexually dimorphic songs, and that both females and males combine their songs to produce duets. Most duets are initiated by males and answered by females. Females have only one song type in their repertoire, while males have multiple song types with a finite repertoire size of 49.7 ± 8.8 (calculated with simple enumeration; n = 8) or 55.4 ± 16.1 (calculated with the capture–recapture technique; n = 19) song types on average per bird. The vocal activity during the morning resembles the pattern of dawn chorus, although individuals usually start vocalising after sunrise, with both sexes contributing to the vocal activity during the morning. We also found that the number of songs that two males share decreases as geographic distance increases between territories, suggesting that males learn their songs from their parents or neighbouring tutors, a learned behaviour important in intra-sexual interactions. Our study adds to the accounts of Neotropical bird species that have detailed vocal descriptions and will facilitate comparisons with other taxonomic groups within the Rufous-naped Wren complex, shedding light on taxonomic disputes.