"Extinct" Woodpecker Still Elusive, But Signs Are Good
for National Geographic News
|February 20, 2002|
The search for the ivory-billed woodpecker is over, with no sightings of
the elusive bird, but lots of hope.
A team of six internationally
known birders combed the forests, bayous, and swamps of the Pearl River
Wildlife Management Area in southeast Louisiana for 30 days in the hope
of finding and photographing the bird.
The ivorybill has been thought to be extinct for the last 50 years. But unconfirmed sightings have intrigued scientists for years, and in 1999 a forestry student reported spotting the bird.
Ornithologists at Louisiana State University (LSU) deemed the report highly credible, so Zeiss Sports Optics agreed to sponsor an intensive search for the bird in the 35,000-acre (14,165-hectare) forest. The Louisiana Department of Wildlife and Fisheries' Natural Heritage Program, LSU, the U.S. Fish and Wildlife Service, and the Ornithology Lab of Cornell University also participated in the search.
"There were three potential outcomes of the 30-day search," said Van Remsen, an ornithologist at Louisiana State University and curator of birds at its Museum of Natural Science. "We could find nothing, in which case the search is over. We could find the bird. Or, the most tantalizing, we could find evidence that the bird might be here.
"It's not only like looking for a needle in a haystack, it's looking for a needle that is moving," he said.
Now, the question of whether the ivorybill is alive and well in the swampy forests of Louisiana has been answered with a resounding chorus of "might be," "maybe," and "definitely a possibility."
Although no one on the team actually spotted the bird, the searchers said they found promising evidence in an area they came to refer to as the "hot zone."
On the afternoon of January 27, ten days after the search started, four members of the team heard and recorded a distinctive tapping pattern that sounded very different from that of the common pileated woodpecker that inhabits the swamps. The signal consisted of four double raps, separated by 20 to 30 seconds, followed by a single rap, followed by four consecutive raps.
The sound is very different from that of the pileated woodpecker, said Peter McBride, a habitat biologist from Washington with extensive field research in several areas of North America and South America. "It was staccato, incisive, and penetrating," he said, "very similar to that of the Magellanic woodpecker in South America, which is in the same genus as the ivorybill."
The birders couldn't get to the source of the sound because of high water, but they concentrated their efforts in that area for the next two weeks. They found encouraging signs of the woodpecker's habitat. A concentration of trees had extensive scaling of bark and several large cavities in dimensions and positions that resemble descriptions by James Tanner.
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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