Turkey vultures have peculiar nesting habitats, study finds
Omnipresent and homely, turkey vultures are a native California wildlife species that doesn't get a lot of research attention.
But UC Cooperative Extension advisor Greg Giusti has found a surprising level of interest from the public in his Northern California research project about turkey vultures' nesting preferences in oak woodland.
“Animals with cute fuzzy faces are far more attractive in our culture,” said Giusti, a wildland ecology expert. “Turkey vultures have been overlooked. Very little is known about their biology and environmental needs.”
In the study area, the researchers counted 417 trees in all; seven of them had suitable nesting elements for turkey vultures. They found that the vultures at the Hopland facility select large hollow trees – either dead or alive, either shaded or in the sun – to lay eggs and rear their young. The tree species in the study included blue oak, interior live oak, Oregon white oak and valley oak.
The nesting trees were widely dispersed and ranged in diameter from 36 inches to 65 inches around at breast height. The nesting cavities are vertical tubes in the tree trunks that drop down as much as 13 feet from the entrance to the ground.
“This is very different from other large birds, like eagles and osprey, who build open cup nests high up in tall trees, which they may use for generations,” Giusti said.
After turkey vulture chicks hatch, the parents drop into the cavity five or six times a day to feed their young, Giusti said. How birds with a five-foot wingspan traverse a deep vertical tunnel is a mystery.
“They just shimmy up and down, I would imagine,” Giusti said. “We don't know how the young birds do it when they fledge. We've never witnessed the adult birds calling them out.”
Giusti said the scientists will continue to build on the turkey vulture nesting database they have started with results from this project. In the coming years, they hope to learn whether turkey vultures will re-use successful nesting sites and whether they may be found nesting in fallen logs or rock piles.
An initiative to maintain and enhance sustainable natural ecosystems is part of the UC Division of Agriculture and Natural Resources Strategic Vision 2025.