Oak tree selection by nesting turkey vultures (Cathartes aura)

Abstract

Turkey vultures (Cathartes aura) are a ubiquitous component of California’s oak woodland faunal assemblage. Though obvious, they are one of the least studied vertebrates found in our hardwood forests. This study attempts to define the role of oak trees as nesting sites for this large avian species. Verified nest trees are evaluated to determine tree structure and morphology, tree size, cavity size and cavity volumes. Nest trees need to be large and old to develop the nest characteristics being utilized by turkey vultures. Nest trees tend to be erect with large trunk cavities that extend to the ground. The entrance location and aspect of the nest cavity does not appear to be a limiting factor in selection. Internal nest cavity volumes vary between 0.80 m³ and 1.55 m³. External tree sizes (DBH) vary between 91.4 cm to 165.1 cm. Selected trees were both alive and standing snags. The project is currently conducting transect surveys across the ownership to determine the relative abundance of potential nest trees based on the information gathered from known nest trees.

Parent Publication

• Proceedings of the seventh California oak symposium: managing oak woodlands in a dynamic world

Citation

Giusti, Gregory A.; Keiffer, R.J.; Feirer, Shane; Keiffer, R.F. 2015. Oak tree selection by nesting turkey vultures (Cathartes aura). In: Standiford, Richard B.; Purcell, Kathryn L., tech. cords. Proceedings of the seventh California oak symposium: managing oak woodlands in a dynamic world. Gen. Tech. Rep. PSW-GTR-251. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 107-110.