Daily movement patterns of the Black Vulture Coragyps atratus in the city of Mérida, Venezuelan Andes

Abstract

The Black Vulture Coragyps atratus is the most abundant vulture in the Americas, but its ecology in the neotropics, particularly in Venezuela, remains poorly known, despite its affinity for urban environments. This study characterized the daily movement patterns, evaluated the influence of environmental variables, and estimated the minimum population size of the Black Vulture in the city of Mérida, Venezuelan Andes. Daily counts were conducted from fixed observation points during October and November over four consecutive years (2021-2024), recording hourly individual abundance, direction of movement, and environmental variables. A cyclical bimodal movement pattern was observed, with a morning peak of mass displacement along the meander belt of the Chama River ascending to the northeast out of the city, and an evening peak of return descending to the southwest. Generalized linear models showed that Black Vulture abundance was positively correlated with temperature and negatively correlated with cloud cover and precipitation. Additionally, net directional counts on days with favourable environmental conditions yielded an estimated population of 614 ± 150 individuals for the city of Mérida. The results suggest that Black Vultures in Mérida use the city and its surroundings as roosting sites and take advantage of orographic conditions and urban thermals to move efficiently towards foraging areas.