Nocturnal Bird Activity and Call Diversity in Benue State Floodplain Forests, North Central Nigeria

This study documents nocturnal bird activity and call diversity in floodplain forest habitats along the Benue River, Benue State, located in Nigeria's North Central geopolitical zone. Nocturnal birds including owls, nightjars, and herons are poorly monitored in Nigerian surveys, yet they perform important ecosystem functions as predators and are sensitive indicators of forest quality. Passive acoustic monitoring was conducted using audio recorders deployed at eight sites in floodplain forest remnants over 60 nights during dry and wet seasons. Recordings were analysed using automated species recognition software calibrated for West African species and manually verified by ornithologists. Call surveys were supplemented by spotlight transects for direct observation of nocturnal species. A total of 19 nocturnal bird species were detected, including seven owl species, five nightjar species, four heron species active at dusk, and three rails. The Barn Owl Tyto alba and African Wood-Owl Strix woodfordii were the most frequently detected species. Call activity peaked in the period two hours before midnight and two hours before dawn. Species richness was significantly higher in larger, less-fragmented forest patches. Three species recorded are classified as near-threatened on the IUCN Red List. The study establishes a baseline acoustic inventory for nocturnal birds in Benue floodplain forests and recommends passive acoustic monitoring as a cost-effective survey method for future long-term biodiversity assessment in Nigeria. Keywords: nocturnal birds, acoustic monitoring, Benue floodplain, owl diversity, North Central Nigeria.