Naveda-Rodriguez A., K.L. Bildstein, D.R. Barber, J.F. Therrien, M.L. Avery, B.M. Kluever, S.A. Rush, and F.J. Vilella. 2023. Turkey Vulture survival is reduced in areas of greater road density. Ornithological Applications 125:duad024.
Abstract
Annual survival of Turkey Vultures (Cathartes aura) may be influenced by landscape heterogeneity and anthropogenic disturbance. We quantified the effects of landscape composition (Shannon’s diversity index) and configuration (contagion, edge density and largest patch index), and human footprint (road density) on the survival probabilities of the three North American breeding populations (western, central and eastern) of Turkey Vultures wintering in the Neotropics during a 17-year period. We used Cox’s proportional hazards models with time-varying covariates to estimate spatial and temporal changes in survival rates of adult Turkey Vultures. Human footprint, but not landscape composition and configuration, influenced survival rates in space and time. Overall annual survival averaged 0.87 (95% CI = 0.74 – 0.98). Mortality risk was low in western and central populations (hazard ratio <1) but was 3.7 times greater for vultures in the eastern population. Risk of mortality for all vulture populations increased with road density, and this was greater during the non-breeding and return migration seasons. The spatial variation in road density across America may generate a network of ecological traps for Turkey Vultures induced to stop in areas of greater road-kill abundance. The negative impact of roads on Turkey Vultures goes beyond the ecological aspect. Roads acting as a magnet for vultures can increase the occurrence of vulture-vehicle collisions and potentially aggravate human-wildlife conflicts. Further analysis are needed to address survivorship and mortality factors of young birds. We emphasize the need for studies focusing on the impact of other linear infrastructures (e.g. railways and power lines) and the management of human-vulture conflicts (through vultures depredation permits) that may can compromise the long term survival of Turkey Vultures and other avian scavengers.