Diel and seasonal variation of Striped Cuckoo
Studying seasonal changes in the vocal activity of birds may shed light on the function of avian vocalizations and the phenology of life history events. Our current knowledge regarding the seasonality of the vocal behaviour of tropical birds in general, and avian brood parasites in particular, is very limited. Here, we employed passive acoustic monitoring with automated signal recognition to monitor the vocal behaviour of the Striped Cuckoo Tapera naevia over a complete annual cycle in the Brazilian Pantanal. We evaluated whether the pattern of vocal activity differed between the two main vocalizations of the species (sem-fim and wee-series songs) and whether vocal activity varied with time of day and season. The diel pattern of vocal activity for both vocalization types showed a bimodal pattern, with the first peak of vocal activity in the few hours after sunrise and the second peak before sunset, in agreement with prior studies in other cuckoos. The sem-fim song was also produced during the night, while the wee-series song was produced only during the day. Both vocalization types showed clear seasonality and were produced between mid-June and mid-February. Seasonal changes in vocal activity suggest that the Striped Cuckoo breeds during the dry season and leaves the study area during the flooding period. The seasonal pattern of the wee-series song showed strong seasonality, with 90% of these calls detected in September and October, whereas the sem-fim song showed weaker seasonality, with 80% of the calls detected during the July–October period. Our study indicates that automated signal recognition might be a reliable tool for monitoring cuckoos. Further research could evaluate whether the different seasonal patterns of the sem-fim and wee-series songs of the Striped Cuckoo are related to different functions.