The whooping crane, the tallest bird in North America, whose numbers dwindled to fewer than 20 in 1941, is not only back from the brink of extinction but also thriving -- a comeback story, federal wildlife officials say, that illustrates how a coordinated conservation effort can save a species. . . .

This year, the nation's only natural wild population of whooping cranes reached a milestone. Stehn's mid-December census of the migratory crane flock at the wildlife refuge, where he is based, numbered 237. Combined with the number of birds in captivity in three special flocks raised for reintroduction to the wild and those in zoos, the crane population now numbers 518. This is the first time in more than a century that whooping cranes have numbered more than 500.