MNN - Mother Nature Network

The United States was once home to a rich and diverse avian population, with birds such as the passenger pigeon, the Carolina parakeet and the dusky seaside sparrow winging through our skies. But several centuries of land development, hunting and human encroachment on habitats has thrown our nation’s birds into crisis, resulting in the extinction of some and threatened status of many. Today, the U.S. Fish and Wildlife Service reports that as many as 91 species of the nation's birds remain on the verge of extinction or are threatened. Here are 10 birds currently under threat in the United States.