As the Woodpecker Flies

April 2008

Searching for Ivory-billed Woodpeckers on foot and by boat in dense, flooded forests takes a lot of time and the odds of being in the right place at the right time to see or hear the bird are slim. Would searching more territory in less time from the air be a better way to get the job done? Biologists hoped to answer that question by conducting helicopter surveys in Arkansas. The flights were funded by the U.S. Fish and Wildlife Service and the Arkansas chapter of The Nature Conservancy.

Scientists and ivory-bill search team members from the Cornell Lab of Ornithology participated in the surveys, along with colleagues from the Arkansas Game and Fish Commission, the U.S. Forest Service, U.S. Fish and Wildlife Service, and The Nature Conservancy. They flew on several flights a day for six days between January 28 and February 4. There were thrilling moments for sure, hanging out of an open-door helicopter 200 feet above the forest canopy, watching eagles, herons, and woodpeckers flying below.

“It’s a unique experience to fly that low over the forest and see all those birds from that perspective—that was cool!” says the Lab’s project scientist Martjan Lammertink.

But the bottom line is this: Using a helicopter specifically to find ivory-bills is not a productive strategy. Aerial surveys depend on the woodpeckers being flushed by the approaching helicopter so the birds can be spotted as they fly away. But few of the woodpeckers along the flight path of the helicopter actually flush, making this an ineffective way to search. The facts and figures to back up this conclusion are part of a scientific paper being prepared by Lammertink and five coauthors for the Journal of Wildlife Management.

Lammertink uses known densities of Pileated Woodpeckers to make the case. “We saw plenty of pileateds from the air, and could even photograph the majority of them as they flushed on either side of the aircraft’s flight path,” Lammertink says. “But what we saw was a small percentage of the birds we know are actually there, based on population-density surveys we’ve done on the ground in previous years. With a bird as rare as the ivory-bill—and if it flushes as infrequently as the Pileated Woodpeckers do—there’s practically no chance of seeing it from the air.”

In other words, any advantage gained by covering a lot of ground with a helicopter is undermined by the fact that so many birds are missed—90% or more in the case of the Pileated Woodpeckers.

On the practical side, it’s very expensive to put a helicopter in the air. “Six searchers on the ground found about the same number of Pileated Woodpeckers per day as the helicopter crew during a day’s flight,” says Lammertink. “You also get a bigger bang for your buck on the ground because the searchers can do other things—conduct playbacks, look for cavities and feeding sign, and count other bird species of interest.”

What the Arkansas helicopter surveys did establish is that large woodpeckers can be seen and photographed from the air. If aerial searches for other purposes are already taking place over potential habitat, then crews should put checking for the ivory-bills on their “to-do” list.

Images (top to bottom): Hovering helicopter, by Abe Borker; Bald Eagle, by Martjan Lammertink; Martjan Lammertink and son Palung, by Utami Setiorini; Helicopter cockpit, by Abe Borker; Flying Mallards, by Martjan Lammertink.

--Pat Leonard