last seen in 1944 the ivory-billed woodpecker (Campephilus principalis) was considered extinct,  however in 1999 a forestry student in the pearl river region of southeast louisiana sighted a strange pair of woodpeckers, who’s description matched that of the ivory-billed woodpecker. then in 2002 an expedition of biologists in the pearl river wildlife management area, discovered signs of large woodpeckers activity (i.e., scaled bark and large tree cavities) and recorded the distinctive "double knock" rapping sound made by the ivory-billed woodpecker.  finally in april 2004, A large woodpecker of the size, wing pattern at rest and in flight, and with white plumage on its back between the wings was videotaped in the cache river national wildlife refuge, arkansas and cited as evidence of a living ivory-billed woodpecker.  cornell university and the nature conservancy quietly and quickly bought up land in this area, closing it off for fear bird enthusiasts would rush to the area disturbing the birds. in the fall of 2006 an "autonomous observatory" of robotic high resolution video cameras with image processing software was installed to detect and record video of birds in flight inside a high probability zone in the cache river area, but as of august 2007 not one ivory-billed woodpecker has been recorded.