DULUTH, Minn. (AP) — Nearly 900 loons and probably more died while migrating south across Lake Michigan last fall, and scientists suspect invasive species may be to blame.

With the iconic birds of the North Country beginning their migration back from the Atlantic and Gulf coasts in less than a month, Minnesota Public Radio reported Monday (http://bit.ly/10CYiYb ) that scientists with the U.S. Geological Survey think a complex interplay of invasive species may be the cause of the mass die-offs.