那只鹡鸰在草地上欢快地跳来跳去，尾巴不停地上下摆动。

The ___wagtail was hopping cheerfully on the grass, its tail constantly wagging up and down.

那个小男孩跑来跑去，像只不安分的鹡鸰鸟。

The little boy ran around like a restless ___wagtail.