The second season of an intensive search for a sought-after North American woodpecker has failed to produce confirmation it still exists.
More than 100 volunteers and experts have been searching for the bird
The spectacular red, white and black ivory-billed woodpecker was long thought to be extinct, but was reported to have been filmed alive in 2004.
More than 100 volunteers and experts spent the winter scouring the woods of eastern Arkansas for the bird.
But they have failed to find further evidence of the bird's existence.
"Certainly we're somewhat disappointed," said Ron Rohrbaugh of the Cornell University Laboratory of Ornithology in Ithaca, New York.
But he added that the lack of evidence "doesn't mean the bird's not there".
Wildlife managers at the Cache River Wildlife Management Area, where the bird was first believed spotted after a six-decade hiatus in 2004, decided to reopen the area for public use after the search came to an end.
The stunning red, white and black woodpecker was formerly distributed across the south-eastern US and Cuba.
The bird carves out a narrow niche for itself by drilling in mature trees.
Logging and forest clearance for agriculture began to impinge on its environment. By the 1920s, it was assumed to be extinct, although, in 1944, there was one more confirmed sighting in North America of a lonely unpaired female, above the remnants of an over-cut forest.
The last confirmed sightings were in the '30s and '40s
Since then, decades of searches yielded nothing and hope gradually faded away.
But on 11 February 2004, Gene Sparling of Hot Springs, Arkansas, was kayaking in a reserve in Big Woods. He saw an unusually large red-crested woodpecker fly towards him and land on a nearby tree.
Experts who conducted their own search finally went on to capture the bird on video, which allowed them to confirm its identity.
But then researchers in Massachusetts said the interpretation of several of the bird's features was "mistaken".
Jon Andrew, the recovery team leader with the US Fish and Wildlife Service, said the search will continue next year across the south-east of the country. Paid and unpaid searchers would look for evidence of the bird in Alabama, Georgia, Louisiana, South Carolina and Texas as well as Arkansas, he added.
The National Audubon Society said it would continue to support search efforts for at least one more year. One volunteer searcher and three members of the public have reported seeing the bird, but none of the full-time researchers has spotted it.
In all four cases, the birds sighted were said to have had large amounts of white feathers on the lower halves of the wings - consistent with an ivory-bill.