I read just recently that in the Ouachita National Forest in Arkansas they've heard the call of an ivory-billed woodpecker. They haven't spotted one yet, but they've heard the distinctive call. That has to mean there's a fair population of them there, but they've been thought extinct for years. Maybe it's like the red wolf here in Texas. For years we thought they were extinct in the state & then a sizeable population of them was discovered in the Big Thicket, within 50 miles or so of Houston. Both that Arkansas forest & Texas' Big Thicket are almost-impenetrable & largely, even today, unexplored. There are simply places in each so dense you either can't get into them or you can't get out of them once you do get in. Nobody knows to this day how many people have gotten lost in the Big Thicket & never found the way out. I suppose with a GPS, if you mark waypoints, you might be able to navigate in places like that, but prior to GPS if you got more than 50 feet off the trail in much of the Big Thicket, you were hopelessly lost.