Groundhogs are herbivores and very timid. The only time I'd worry about them is if they're tunneling under your coop/run. In that instance I'd not worry about the groundhogs doing harm, but any other animals using their tunnels to get in.
The sooner you fix it up, the better for your birds. I'm glad you finally know what's been causing all the trouble!
That's a groundhog. It's just a big one.