Happens all the time?
I don't know about that---I've been bird hunting now for over a decade and it hasn't happened to me or to anyone with whom I hunt. But that's because we're careful enough not to draw a bead on anything below eye level, lest you run the risk of hitting the dog mid-point or mid-flush.
There is no excuse for what Dick Cheney did. None.
I don't know about that---
I'm not a quail hunter. I wouldn't know. Never much been interested in shooting birds. I prefer, or rather preferred, different game. These days, I'm pretty much on the sidelines of most outdoor sports.
But, the people I quoted, definitely qualify as anciently experienced. So, it probably happens a bit more frequently than folks might think.
There is no excuse for what Dick Cheney did. None.
We are agreed. Cheney probably does too. :-)