As spring progresses, the ice and snow of the northern forest zone melts.
春天继续前行，北方森林地区的冰雪开始融化。
The layer of permafrost beneath prevents water draining away.
下面的永冻土层阻止了水的流失。
And the area becomes a vast wetland.
这一地区变成了大片的湿地。
Finland alone is home to 200,000 lakes.
光芬兰就有二十万个湖泊。
These are rich in food and a prime location for nesting birds.
这里食物丰富是鸟类筑巢的绝佳地点。
A haunting call echoes through the morning mist. Red-throated Divers.
幽灵般的叫声在晨雾中萦绕。是红喉潜鸟。
They've just flown inland from the coast to take advantage of the lake's bounty and to nest.
它们刚从海边飞到内陆来，利用湖区的丰富资源，并在此筑巢。
Their plaintive of wail serves as a mating call and helps them claim a territory.
这种哀号是交配的信号，同时宣称领地的归属权。

Courtship is beautifully choreographed, a synchronized swim.
求爱仪式像是经过精美的编排，一种同步的水上舞蹈。
Intruders are threatened and chased away.
入侵者受到威胁、被赶走。
Even in this place of plenty, a choice territory is worth a battle.
就算在这样富足的地方，好的领地也值得用战斗去维护。