The knock-knock sounds recorded and replayed with such hope last January by ornithologists searching for ivory-billed woodpeckers turn out not to be bird noises at all. They’re gunshots, according to researchers at the Cornell (N.Y.) Laboratory of Ornithology.
An international team of bird experts spent a month last winter combing Louisiana’s Pearl River Wildlife Management Area for signs that the charismatic woodpecker, which had not been seen for years, had somehow escaped extinction (SN: 3/2/02, p. 141: Encouraging signs but no woodpecker). On Jan. 27, searchers recorded pairs of loud raps, as if a huge woodpecker were drumming on a hollow tree.
The Cornell lab has analyzed digital recordings from 12 round-the-clock microphones on trees in the Pearl River region. Audio experts found the rapping noises all right, but they were clearly gunshots, says lab director John Fitzpatrick.
He and his colleagues studied the recordings using a computer program that presents sounds as visual patterns. “There was a big, thick vertical line and then a big smudge,” says Fitzpatrick. “Woodpecker drumming looks small on the screen in comparison to a gunshot.”
The researchers also fed the 4,000 hours of recordings through programs that automatically check for certain sounds. Other scientists have used such programs to find whale songs in ocean recordings and elephant rumbles in African forests. The Cornell laboratory prepped the program with recordings of real ivory-billed woodpeckers made during the 1940s. In the Louisiana recordings from last winter, however, the programs found neither ivory-billed woodpecker calls nor raps.
“We have not given up,” says Fitzpatrick. He acknowledges that the searches are long shots but says he plans a few more and is even considering another round of recording near the Pearl River.