题目解析:
作者的目的是强调该地区作为鸭子繁殖地的价值。提示:...serves as an important breeding area for more than 300 bird species, including large numbers of migrating shorebirds and waterfowl; Every spring, birds arrive in great numbers…to mate in the seasonal wetlands..., Prairie pothole country produces half of North America’s 35 to 40 million ducks. ...