During a long-term study at the Desert Tortoise Research Natural Area in the western Mojave Desert of California, factors affecting the decline of desert tortoises were evaluated inside the protective fence vs. outside. During the five-survey years, 1,645 sightings of 13 species of avian predators were collected. Eleven species occurred both inside and outside the fenced Desert Tortoise Research Natural Area, and two species, the short-eared owl and great horned owl, occurred only inside the fence. The most abundant predator was the common raven with more observations outside the fence than inside the fence in most years. Ravens are hyper-predators of the desert tortoise and, at the Desert Tortoise Research Natural Area, are one of four drivers of population decline. This species also inhibits recovery because of the high numbers (Berry et al. 2020, Wildlife Monographs 205:1-53). References: Berry, K.H., Yee, J.L., Shields, T.A. and Stockton, L., 2020. The Catastrophic Decline of Tortoises at a Fenced Natural Area. Wildlife Monographs, 205(1), pp.1-53.