Following the air currents they circle upward, then suddenly slide off to one side as if they had gone out of control, but just in time they adjust course. Nevertheless, often one or two leave the group and take off on their own.
它們隨著氣流愈盤愈高，突然往外一滑，彷彿失「翼」出軌，卻又及時修正；然而屢屢有一兩隻會離群單獨行動。