Predator attack or birds picking on each other?

[Lilyofsalen]

Thanks everyone, I think whatever it was that dug that hole (I'm thinking mice since I saw them beside the aviary before) is gone. I dug up that edge, dropped a brick in front of where they had squeezed beneath the foundation, and buried it. I really think it was a mouse because there's just no way a rat would've been able to squeeze beneath the board and go through 1/2 inch mesh.
Also, I think I figured out how things went down. I think my quail panicked when they saw the mouse and one of them flushed hard into the mesh of the aviary about 4 feet up on one side. At that spot in the mesh, there was a single primary feather with a bloody quill and beneath a puddle of blood. I think they just freaked out and some of them hurt themselves.