Does anyone know anything about Walnut trees and whether or not they are toxic to chickens? I'm pretty sure we have a large Black Walnut tree in our yard adjacent to the chicken run. I'd like to let the birds into that part of the yard but I'm worried eating the leaves may make the birds sick. Does anyone have any experience with these trees? Or... is this even a Walnut?

A close up of the leaves.

Thanks in advance!
A close up of the leaves.
Thanks in advance!