The birds rose and dip in their flight.

鸟儿一上一下地。

Hesperornis is an extinct genus of flightless aquatic birds that lived during the Late Cretaceous.

黄昏鸟是一种已经灭绝不会鸟，生活在白垩纪晚期。

His imagination paints himself hovering in the sky.

他想自己在天空。

Birds fly in the air.

鸟在空中。