If your strategy is to flush and shoot in flight, 20ga semi-auto with modified or tighter choke and #6 shot is the perfect choice. If you prefer to get them while roosted in a tree or still on the ground beside the road, a .22 or .17HMR to the head is very satisfying (assuming competent marksmanship). If you're not sure, use the 20ga with modified choke and #6 shot and pay attention to pellets in the meat.