Johannes Fritz, an Austrian biologist, needed to come up with a plan again if he was going to prevent his rare and beloved birds from going extinct.

To survive the European winter, the northern bald ibis needs to migrate south for the winter over the Alps. But shifting climate patterns have delayed when the birds begin to migrate and they are now reaching the mountains too late to make it over the peaks, locking them in an icy death trap. Determined to save them, he decided to teach the birds a new, safer migration route by guiding them himself in a tiny aircraft. He was confident that he could succeed in this daring, unconventional plan.

Some 400 years ago, the Europeans hunted these birds without stopping and devoured the last in the wild, causing the birds to disappear entirely from the wild. When Mr. Fritz was born 56 years ago, the northern bald ibis could be found in Europe only in captivity（圈养）.

Mr.Fritz has spent his career reintroducing the birds into the wild. Through years of trial and error, he learned to fly like a bird. He modified（改装）a lightweight aircraft so it would fly at speeds slow enough for the birds to keep up. In 2004, he led the first flock from Austria to Italy, and has since led more migrations. But the route he originally taught the ibises does not work successfully. With climate change warming the area where the birds summer, they now start their migration at the end of October instead of the end of September. The trip is expected to take about six weeks, "Still, we're optimistic that it'll work," said Mr. Fritz.

His family and colleagues witnessed the risks he was taking. "But the unavoidable risks are necessary," Mr. Fritz said. "It's not so much a job, but my life's purpose."