By Tobias Carroll Since the early 1980s, the comeback of the nation’s bald eagle population is one of the environmental movement’s most notable success stories. That doesn’t mean that eagles aren’t still in danger, however — from a host of variables, including some environmental factors, that remain risky to the nation’s national bird. Among them is something that will sound deeply familiar to most readers: eagles are presently dealing with a pandemic of their own. A recently-discovered bird flu, H5N1, has had a dramatic effect on eagle populations since the beginning of the year. A new report…