Have you ever been around a Hawthorne tree? They are not a tree you want in your yard. The thorns are sharp as needles and tough as nails. They will rip holes in mower tires, your clothes, and you.
Somehow sparrows jump from branch to branch and the thorns never bother them. It was interesting to watch.
I read that many birds actually prefer thorny plants and that hawthorn trees are excellent for attracting them. Nature must have given them special ways of dealing with the thorns.