Hope Knocks

Thousands of hours of recordings yielded some intriguing sounds.

By Mike Powers

On the second floor of the Johnson Center for Birds and Biodiversity, there is a small, easily overlooked conference room. Most people assume it's for storage and walk by without a second glance. For more than a year, it's been an ideal hideaway to analyze sound recordings, searching for evidence of Ivory-billed Woodpeckers in the Big Woods of Arkansas.

Inside the room, as many as seven sound analysts sit at computers, surrounded by topographic maps and aerial photos on the walls that pinpoint where sounds were recorded. Images of White-breasted Nuthatch and Blue Jay, species known to make calls similar to the Ivory-billed Woodpecker, remind us of the other wildlife we encounter as we listen to the recordings; photographs of towering swampy forests put us in the right frame of mind. Because our mission was initially cloaked in secrecy, images of ivory-bills were tucked behind data sheets hung on the corkboard. As we recorded our data, a quick flip to these images inspired us to keep listening for our target species.

The inspiration started to fade after weeks of finding nothing of real interest. Then, one morning in February 2005, Beth Howard, who had been scrolling through recordings made during the dawn and dusk hours of late December, played a short segment, seemingly devoid of sound. The screen appeared mostly blank except for two small peaks followed by what looked like the sail from a boat.

A few seconds later I realized the nondescript twin peaks were extraordinarily significant. With each replaying of the loud BAM -bam! recorded on December 25 (what a Christmas present!) it was clear they were extremely similar to the display drums of species in the same genus (Campephilus), the Pale-billed and Powerful woodpeckers from Central and South America. The sail-like pattern following the double knock is a gunshot. (In the duck-hunting area where the sounds were recorded, gunshots are common.)

When acoustic team leader Russ Charif quickly analyzed the two peaks, he found that they fit a Campephilus double knock. The time of day was right: dusk, when ivory-bills are reported to give a double-knock before entering a roost hole for the night.

We sought input from the search team. Project manager Ron Rohrbaugh was the first to sit and listen. When the knock filled the room, he nearly jumped up. Seeing Ron get that excited caused my heart to skip a beat. Before, we wanted to believe it was an ivory-bill; now it seemed it really could be one.

We asked three additional search team members to listen to the soun--Conservation Science director Ken Rosenberg, Cornell Laboratory of Ornithology director John (Fitz) Fitzpatrick, and Living Bird editor Tim Gallagher, whose sighting of an ivory-bill the previous year had led to the Lab's involvement in the search.

Mike Powers and Lab director John Fitzpatrick examine acoustic data from recordings that resemble the calls of Ivory-billed Woodpeckers.

Photo by Tim Gallagher/CLO

Fitz arrived shortly and sat in a chair facing the screen, head down, eyes closed, focused. After the double knock again filled the room, Fitz raised his head and looked around, uttering "Holy mackerel!" He didn't have to say much more: that reaction pushed our excitement off the chart.

Over the next couple of hours, Ken and Tim arrived to listen, and Ron and Fitz joined them to analyze and discuss the sounds. We also clipped and emailed the sounds to colleagues in Arkansas for their thoughts and input. So far we aren't able to exclude other possible sources for these sounds, but everyone agrees they are of high interest. Continued searching has turned up many more intriguing sounds.

Our excitement waxes and wanes as we find these additional knocks as well as promising recordings that sound like kent calls. It grows as we realize we may be listening to recordings of a bird frequently written off as extinct, but wanes after days of not finding anything new or definitive.

Because there are other sources that can make double knocks (branches, other woodpeckers, gunshots), it may be that we can never say with 100 percent certainty that any recorded double knock was made by an ivory-bill. The kent calls may be the only way to acoustically determine the presence of ivorybills. As of this writing we are trying to see if a Blue Jay could be the vocalist. We've heard Wild Turkey, Red-winged Blackbird, Common Moorhen, American Coot, and even Great Blue Heron calls that are deceptively similar to the ivory-bill recordings we have from 1935. But with each new sound that invites a second (and third and fourth) listen, a startled jump, an unsuppressed oath, or a spirited debate, hope for this bird continues to knock.

Mike Powers is the acoustic analysis coordinator for the Lab's Ivory-billed Woodpecker Research Project.

For permission to reprint all or part of this article, please contact Laura Erickson, editor, Cornell Lab of Ornithology, 159 Sapsucker Woods Rd., Ithaca, NY, 14850. Phone: (607) 254-1114. email: lle24@cornell.edu