1、During flight, birds rely on the synchronized wingbeat to generate lift and propel themselves forward.
飞行过程中，鸟类依靠协调的翅拍来产生升力并向前推进。

2、The speed and frequency of a bird's wingbeat can vary depending on its size, species, and flight behavior.
鸟类的翅拍速度和频率会根据其大小、物种和飞行习性的不同而有所变化。