Some scientists still believe the ivory-billed woodpecker exists in the Big Woods, but they haven't been able to capture a sharp image of its remarkable 30-inch wing span and glossy black and white feathers on film or video camera.
To date, searchers have investigated about 83,000 of the 550,000-acre woods that swallow up the Cache River National Wildlife Refuge. The refuge is where kayaker Gene Sparling spotted the bird Feb. 11, 2004, and Cornell University experts said they made subsequent sightings.
Engineer David Luneau caught a blurry image of what some believe is the "Lord God bird," the third-largest woodpecker in the world, on video in 2004. Others challenge the claim that the ivory bill survived decades of clearing forests for farming, timber, roads and towns.
"Since early 2005, none of our group nor anyone from the public that we are aware of has made a definitive absolute sighting of an ivory-billed woodpecker that we can document with a photograph or a sound recording," said Ron Rohrbaugh, project director at the Cornell Lab of Ornithology.
According to researchers, it became known as the "Lord God bird" because people, upon seeing it, would exclaim, "Lord God, look at that bird!"
The Big Woods is a hot, humid place - tupelo, cypress and oak bottomland filled with mosquitoes, poisonous cottonmouths and thigh-high swamp water. The swamp is so thick with vegetation that scientists concentrate their work on the months when leaves are off the trees - and the temperatures are bearable. They target areas where they have reports of credible sightings.
Wildlife biologist Allan Mueller said he saw an ivory-billed woodpecker during a search in May 2007. But it happened so quickly he missed getting the bird on camera.
"We were hearing calls, we were hearing the double-knocks, which is a distinctive way that the ivory-bill woodpeckers have of knocking on a tree," he said. "It's just two very quick knocks on a tree. Bam. Bam."
To the untrained eye, the ivory bill can be mistaken for a pileated woodpecker. Past research suggests the ivory bill ranges as much as six miles from its roost while searching for succulent beetle larvae, its favorite food.
Others outside the search team had reported sightings, said Mueller, avian conservation manager for The Nature Conservancy in Arkansas. So he and his teammate decided to get out of the boat and investigate. While his partner searched from the bank, Mueller walked into the woods.
"I saw a large bird, large woodpecker, flying directly toward me," he said. "All I know, what I knew then, was this is a big woodpecker coming at me. So naturally I paid attention.
"Probably about 100 feet away from me, it did a complete U-turn. And when he did the U-turn he flew out into a sunny area where I was able to get a very good look at the top of the bird, the top of the wing with a black, very glossy, shiny, black front and very white bright trailing edge of the wing. And just that quickly it was over."
When then-Interior Secretary Gale Norton announced in 2005 the rediscovery of the bird, she and then-Secretary of Agriculture Mike Johanns pledged federal dollars from existing funds to research the woodpecker, restore its habitat and develop a recovery plan as required by the Endangered Species Act.
To date, about $9.6 million has been spent toward those goals, including nearly $2 million to search the woods in Arkansas and other states. Researchers say the bird also has been seen and heard in the swamps of northwestern Florida.
Despite challenges from fellow scientists, many searchers remain convinced the bird has cheated extinction.
"It always has been one of these icons of the birding world, an icon of the deep woods. It has this amazing place in people's minds and hearts," said Laurie Fenwood, the ivory-billed woodpecker coordinator for the U.S. Fish and Wildlife Service in Atlanta.
