Arctic terns begin their migration in the Northern hemisphere in the summer, which is breeding season.

北极燕鸥在夏季开始在北半球迁徙，这是繁殖季节。

Back in 2010, an international research team fitted tracking devices to birds they believed to be special — Arctic terns.

早在 2010 年，一个国际研究小组就在他们认为很特殊的鸟类——北极燕鸥身上安装了跟踪设备。

But one species, the arctic tern, flies to northern Europe all the way from the Antarctic. No animal on earth migrates this far.

而有一种鸟类，北极燕鸥，却从遥远的南极洲一路飞抵北欧，地球上没有任何动物能迁徙这么远。

This means that arctic terns can rack up over 2 and a half million kilometers of flight in a lifetime — enough for three round trips to the moon.

这意味着北极燕鸥一生可以积累超过 250 万公里的飞行距离，足够三次往返月球。