Poleward expansion of Turkey Vultures (Cathartes aura) under future conditions

With rapid global change in the Anthropocene, it is important to understand and predict changes in species distributions that could potentially impact entire ecosystems. Turkey Vulture (Cathartes aura) distribution has been expanding and, as an obligate scavenger, its presence can have an impact on the ecosystems it inhabits. Here we investigated the relative impact of human population density and climate (temperature and precipitation) on Turkey Vulture presence. We used eBird community science data from 2010-2020 to create a species distribution model for Turkey Vultures across their entire range using a Random Forests algorithm. We then projected this distribution for the year 2070 to estimate any changes. Our model predicted an expansion in Turkey Vulture distribution during the breeding season of May-August. This suggests that areas of both North and South America where only seasonal, migratory Turkey Vultures currently exist can expect resident populations of Turkey Vultures in the future. Mild temperature was an important variable for presence during the nonbreeding season, whereas low human density was more important for predicting presence during the breeding season. The distribution of Turkey Vultures is widest during the breeding season, meaning that factors influencing the breeding range could be considered more important when considering range expansion. As such, our findings suggest that warmer boreal winters coupled with the potential presence of domestic carcasses in agricultural areas (i.e., low human density) are facilitating Turkey Vulture range expansion. This expansion has important implications for the scavenging community in northern latitudes where increased Turkey Vulture presence might impact other species relying on carrion.

Automated summary

With rapid global change, understanding and predicting changes in species distributions are crucial. In this study, the impact of human population density and climate on the presence of Turkey Vultures was investigated. The model predicted an expansion in Turkey Vulture distribution during the breeding season, indicating possible resident populations in areas where only seasonal, migratory Turkey Vultures currently exist. Mild temperature and low human density were important factors for presence during different seasons. The findings suggest that warmer winters and the presence of domestic carcasses facilitate Turkey Vulture range expansion.