Even though the land is still frozen, to some, this is the breeding season.
虽然地面依然冻着冰，却到了一些动物的繁殖季。
Whooper Swans have arrived.
大天鹅飞来了。
They may have spent the winter in central or eastern Russia, thousands of miles away.
它们可能在远在数千英里之外的俄罗斯中部或东部过冬。
These swans mate for life and return to the same place each year to breed.
大天鹅是终生一个配偶的，且每年都回到相同地点繁殖。
This noisy display lays claim to their patch and serves as a warning for others to stay away.
这种嘈杂的表演是在宣称自己的领地，同时警告其它天鹅离远些。
Good territory is hard to come by.
好地盘不容易碰到。
Another pair have moved in.
另一对天鹅靠近了。
The head-down display is a warning and a challenge to a duel.
这种头朝下的姿势是一种警告并要求对决。
Whoopers are among the largest of all swans.
大天鹅是最大的天鹅之一。

Their vicious battles could easily result in a broken neck or wing.
它们之间凶猛的对决极有可能扭断脖子或翅膀。
For once, the female doesn't just stand by.
这回，雌性没有袖手旁观。
She joins in the fight.
它加入战斗。
The intruders are driven away and the territory holders continue proclaiming their rights.
入侵者被赶走，领地所有者继续宣告自己的权利。