Tanner tracked the bird from 1937 to 1939 in a tract of northeastern Louisiana (now mostly the Tensas National Wildlife Refuge) and wrote the bible on the bird, providing most of what is known today.
The bark-scaling is consistent with what is known about ivorybills. The woodpeckers peel large chunks of bark off of dead trees while foraging for insects. They tend to pick trees that have been dead for less time than those visited by pileated woodpeckers, and the tree cavities, which were 25 to 75 feet (7.6 to 23 meters) off the ground, are larger than those created by the pileated woodpecker.
But all of this is suggestive, not conclusive, the team reported.
"The main problem is that no one in the world has definitive information on all the sounds an ivory-billed woodpecker can make," said Alan Worthington, a team member from Canada who has served on the American Birding Association Checklist Committee and the editorial board of North American Birds.
But the six-person team was highly familiar with woodpeckers, and everyone agreed that the sound they heard didn't sound like that of a pileated woodpecker, Worthington said. "The recording is incredibly impressive," he added, "and it's a sound I haven't heard in 34 years of birding."
The Louisiana Department of Wildlife and Fisheries won't say where the searchers looked or where the "hot zone" is, to protect the birds. A moratorium on logging was introduced after the possible sighting in 1999 and remains in effect.
McBride recorded more than 100 hours of sounds and will listen to the audio tapes in the next month, in the hope of hearing the bird's cry. A dozen acoustic monitors were stationed in the forest by the Cornell Lab of Ornithology, and after mid-March the data will be collected and analyzed.
In the meantime, the searchers will continue puzzling over key questions such as why the double raps they heard came only from the "hot zone," why they didn't spot the magnificent ivorybilland, of greatest interest, whether the bird is indeed alive and well in the bottom-hardwood forests of Louisiana.
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