I would wait until his head is turning one side or the other and he is bending his knees in a down ward motion. This happens in a blink of eye or less,lol. They dig in for a full speed turn, like a crazy on a dirt bike doing a 180, low sharp dirt fly'n turn. Most shots are missed like this because we always forget, they drop down 6 to 8 inches and we shoot over, to busy thinking about the lead on the shoulder. Now, for me too riskie of a shot. Tall grass always messed up my shots But, if you are one of those bow hunters that can drop geese on the fly, it's a give me!