Movements of Turkey Vultures Provide Evidence of Nonmigratory Behavior and Natal Philopatry in a Population Breeding in Southwestern California, USA.

Turkey Vultures (Cathartes aura) are typically partial migrants but thought to reside year-round in southwestern California, USA. Yet relatively little is known about their movements and breeding biology in the region. Here, we report our initial findings on the movements of 23 Turkey Vultures fledged from six southwestern California nests and patagial-tagged between 2017 and 2023. We hypothesized that resightings of these individuals would show that Turkey Vultures fledged from this region are found: (1) year-round in southwestern California, confirming their behavior as residents, and (2) near their natal nest area during the breeding season when they are sexually mature. To test these hypotheses, we analyzed the locations of these resightings to determine vultures' movements as they related to age and season. The tagged Turkey Vultures were resighted 102 times between 2018 and 2024, at an average distance of 23 km ± 25 km ([SD]; median = 17 km) from their natal nest. Few observations were >100 km from the natal nest, and none were further north than Ventura County, California, or further south than San Diego County, California. All sightings were in a region that was similar in landscape and climate to the natal nest study area. Distance from the natal nest varied with bird age and season: in the spring adult birds were closer to their natal nests compared to younger birds. Overall, the resighting data suggest that Turkey Vultures fledged in southwestern California are year-round residents. Our findings also provide some evidence of natal philopatry in this breeding population, as indicated by the resightings of birds tagged in the region near their natal nest, particularly the adult birds during the breeding season. However, future studies that observe the breeding behavior are needed to fill critical gaps in our understanding of the breeding biology of this species. [ABSTRACT FROM AUTHOR]