turn their wings in both directions.

它们实际上能向两个方向扇翅膀
They can turn them upside down and that's shown in this diagram here,

它们能把翅膀翻转过来如图所示
that they can make the wing go backward and forward,

因此它们能使翅膀向前扇也能使翅膀向后扇
and turn it right side up and upside down,

可以把翅膀翻转上来再翻转下去
so they can create a motion

因此造就了一种运动
where they're creating no net forward thrust or backward thrust,

其中产生的合力既不向前也不向后
but always creating lift

但能一直产生升力
because they're changing the position

因为它们在不停变换
or the orientation of their wings.

翅膀的位置或者说扇动的方向
More complicated than that, if you're interested

实际情况还要复杂些如果你感兴趣
I'm sure you can find information on it,

我确定你能找到更多有关内容
but again they can do this

但蜂鸟之所以有这种能力