This is why it winds me up no end when I see people with .22LR's shooting into trees. The only thing I would ever shoot into a tree is a 12ft/b air rifle, and even then only if i know there are atleast a few hundred yards of farmland behind.
With any firearm, I only take shots from an elevated position and only soft ground, like grass. I've moved away from bipods for this reason now, with sticks you're giving yourself even more of an edge to make sure your angle is always going to strike the ground.
To be honest, i just don't take the shot half the time, or should I say, I spend so long assessing the safety of the shot that half the time I miss my chance to take it. But that's fine. better to be safe than sorry. There will always be another pigeon, rabbit or deer!!
