英语听力：自然百科 黄石公园的夏天 Yellowstone—8

 This pack seem prepared to allow their young a brief foray to experience the world beyond their den¹.

 

Even in Yellow Stone it is extremely rare to see wolf pups like this.

 

Before long they are summoned back into the forest by the pack. It will be winter before they are regularly seen again.

 

As May turns to June, Yellow Stone sees its nursery season. 

 

By early June, summer is finally here. In the flower meadows, plants turn sunlight into the sugar of nectar, and that's what Yellow Stone's smallest migrating bird has been waiting for. The Calliope Hummingbird² has made the journey all the way from Mexico. He’ll make this flower patch his own. And he’ll fight to defend it. He’ll even take on a far larger Rufous Hummingbird.

1 den   

n.兽穴；秘密地方；安静的小房间，私室

参考例句：

• There is a big fox den on the back hill.后山有一个很大的狐狸窝。
• The only way to catch tiger cubs is to go into tiger's den.不入虎穴焉得虎子。

2 hummingbird   

n.蜂鸟

参考例句：

• The hummingbird perches on a twig of the hawthorn.小蜂鸟栖在山楂树枝上。
• The hummingbird is the only bird that can fly backward.蜂鸟是唯一能倒退向后飞的鸟。