Diet of the Great Horned Owl Bubo virginianus nigrescens (Strigiformes: Strigidae) in the Northern Andes of Ecuador and a Literature Review of the Subspecies Dietary Patterns

Abstract

Understanding the feeding ecology of top avian predators is crucial to unravelling trophic interactions and informing conservation strategies. Great Horned Owl Bubo virginianus, among the most widespread nocturnal raptors in America, remains understudied in the northern Andes. We investigated the diet of the subspecies B. v. nigrescens in an inter-Andean valley of northern Ecuador and compiled a literature review of its dietary patterns. Fifty-four pellets collected from 2014 to 2017 yielded 106 prey items. Mammals constituted the primary food source in frequency and biomass, with the Andean White-eared Opossum Didelphis pernigra and Black Rat Rattus rattus dominating the total biomass. Smaller native and introduced rodents were also common, while birds, bats, frogs, and Scarabaeid beetles appeared less frequently, underscoring the owls generalist foraging. A new record of predation on a young domestic cat highlights its adaptability to urbanised landscapes. Our literature review reveals similar trends across Colombia and Ecuador, with mammalian prey--often lagomorphs in higher elevations--dominant throughout. These findings suggest that B. v. nigrescens exhibits a flexible feeding ecology, capitalising on native and non-native prey. However, shifting land-use practices may affect prey availability and pose future challenges for this apex predator. Year-round and multi-elevation studies would help clarify seasonal variation and broader ecological dynamics, guiding conservation efforts in tropical mountain ecosystems.