Biotic and abiotic influences on vocal activity of tropical screech-owl (Megascops choliba) and spectacled owl (Pulsatrix perspicillata)

Abstract

Knowledge of owls' vocal activity is essential for understanding their responses to environmental change. We investigated patterns of vocalizations in the tropical screech-owl ( Megascops choliba ) and the spectacled owl ( Pulsatrix perspicillata ) in forest patches in the far north of the Atlantic Forest, Brazil, from September 2022 to January 2023. We sampled 88 sites in 11 patches using autonomous recording units over three consecutive days. We used static occupancy modeling to estimate the detection probability and, consequently, vocal activity throughout the night, and to test the influence of biotic and abiotic variables on vocal activity. We obtained a total of 3,432 h of sound recordings. Megascops choliba vocalized more frequently at 07:00 p.m., 01:00 a.m., and 04:00 a.m., with most vocalizations occurring from four hours before sunrise until sunrise. We could not support variation in the vocal activity of P. perspicillata throughout the nighttime hours. The vocal activity of M. choliba was negatively influenced by air temperature and was positively influenced by understory density, while the vocal activity of P. perspicillata was negatively influenced by moonlight. Understanding peak owl vocal activity and species-environment relationships will enable more efficient monitoring with limited resources.

Bibliographic Information