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 has thrown our nation’s birds into crisis, resulting in extinction for some and threatened status for many. Today, the U.S. [skipwords]Fish[/skipwords] and Wildlife Service reports that as many as 91 species are threatened or on the verge of extinction. Here are 10 birds currently under threat in the United States, including the Hawaiin geese pictured here. (Text: Katherine Butler)