I know the red maple leaves are and the Sycamore tree is in the maple family. I can't seem to find the answer to this.
I've always known sycamores to be considered safe for horses. Just to be sure I wasn't giving you bad advice, I googled it and found this:
Native North American sycamore trees actually aren't in the Acer species of maples like some other sycamores of the world.
Don't fall for a girl who fell for a horse just to be number two in her world... ~EFO