MADISON, Wis. — When he was a little boy roaming the forests and marshes of Illinois, Rick Lindroth adored catching frogs and climbing trees. His dream came true when he became a full-time scientist, paid to make observations in nature. Even when he’s not officially on the job, with binoculars dangling from his neck, he will effortlessly spot a bald eagle’s nest from his fly-fishing stream in Big Spring valley.