What did one Ivory-billed say to the other?
Cornell University ornithologists have now analyzed 18,000+ hours of audio recordings (which I suspect is the tip of the audio-iceberg for them) collected from 153 different sites within the Big Woods of Arkansas where the Ivory-billed woodpecker (Campephilus principalis) was observed during 2004. They've discovered that the recordings offer additional support for the presence of Ivory-billed woodpeckers in the region. From the Cornell Lab's press release:
The researchers announced the results at the annual meeting of the American Ornithologists’ Union in Santa Barbara, Calif., on Aug. 24, 2005, and invited the public to listen to the calls and knocks on the Web at www.birds.cornell.edu. The sounds are strikingly similar to those made by ivory-billed woodpeckers, the researchers said. One of the recordings, from January 24, 2005, captured a distant double knock, “Bam bam!” followed by a similar and much closer double knock 3.5 seconds later—possibly the drumming displays of two ivory-billed woodpeckers communicating with one another by rapping on trees.
After eliminating thousands of noises from gunshots and other sources, the researchers found about 100 double knocks that bear a strong resemblance to the display drumming of the ivory-bill’s closest relatives. The sounds were clustered around certain recording locations at certain times of day—a pattern that would not be expected if they had been produced by random noises.
Then ARUs also recorded nasal tooting calls similar to those of ivory-billed woodpeckers. Charif said blue jays are notorious vocal mimics that sometimes utter calls like those of ivory-bills. However, he added, a sophisticated acoustic classification program categorized nearly all of the unknown calls from Arkansas as most similar to ivory-billed woodpecker recordings. None matched up with “tooting” calls of blue jays from the Lab’s audio collection, but the researchers say they cannot rule out blue jays until they analyze more variants of the calls.
“We’re excited and encouraged by the acoustic analysis,” said Dr. John Fitzpatrick, director of the Cornell Lab of Ornithology. “These sounds give us additional hope that a few ivory-billed woodpeckers do live in the White River and Cache River region. But this species is still on the verge of extinction and huge mysteries remain to be solved. Certainly, we have a lot more work to do before we know enough to determine its population size, let alone ensure its survival.”
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