Break barrel air rifle. Some .177 run at 1250 fps with lead. And, they push 1400(+) with alloy. Poppin' 'em in the butt makes 'em buck pretty darned hard. However, even that's against the law. And, it seems that I have two neighbors that put me on 24/7 surveillance.
I have some airsoft single pump repeaters. They're pretty weak, but they can get a hen to squawk. My second-to-the-last batch of pullets loved to jump the fence from their run. Popping them with an airsoft when they were on top of the fence, ready to jump to the other side, broke them of the habit.
I'll have to look into the CO2 powered ones. They sound like a blast.