Double Gunshots

Two gunshots in a row may sound like double knocks of Ivory-billed Woodpeckers. Because the autonomous recording units were deployed in duck-hunting areas, gunshots are common sounds on the recordings.

Spectrographic analysis can help identify whether the sounds were made by guns. Gunshots have a wide band of frequencies, followed by a tapering "smudge" representing reverberations of the sound through the forest.

Gunshots from the Pearl River area, Louisiana

The sonogram below is from a recording made during the search for Ivory-billed Woodpeckers in the Pearl River, Louisiana, in 2002. Researchers in the field thought they might have heard the double knock of an Ivory-billed Woodpecker, but acoustic analysis showed the sounds were gunshots. Read the story.