The rainbow smelt fills the local steam as the ice gradually disappears, and the wood frogs start to sing in pools after being frozen for the winter. A family of birds rules our skies and flies over the lake.

老实说，有点偏，不查字典谁也不知道意思，不过不影响整个文章理解。可以看到这里都是描写小动物的，而the rainbow smelt指的是一种鱼类，

以下对the rainbow smelt这种鱼类的描述摘自维基百科：

The rainbow smelt (Osmerus mordax) is a North American species of fish of the family Osmeridae. It was introduced to the Great Lakes, and from there has made its way to various other places.