A northeast Iowa ornithologist’s research has led to the designation of the state’s first Globally Important Bird Area.
Research conducted by Jon Stravers of McGregor, who for seven years has been documenting unsuspected throngs of increasingly rare cerulean warblers in remote bluffs and ravines along the Upper Mississippi River, was the decisive factor in the designation, according to Iowa Audubon President Doug Harr.
“We couldn’t have even applied without Jon’s research,” said Harr, who retired three years ago as coordinator of the Department of Natural Resources’s Wildlife Diversity Program.
“It’s a real feather in Iowa’s and Iowa Audubon’s cap. We have 91 important bird areas, sites deemed critical to declining bird species, and this is the first to get the international recognition,” Harr said.
Iowa Audubon, the National Audubon Society and Bird Conservation International recently announced the honor for the DNR’s Effigy Mounds-Yellow River Forest Bird Conservation Area.
The unit covers more than 14,000 acres of public land that includes Yellow River State Forest, Effigy Mounds National Monument, Pikes Peak State Park and the Bloody Run and Sny Magill-North Cedar state wildlife management areas.
It also encompasses thousands of acres of surrounding private land that provides good bird habitat.
“We all know this is the good stuff. We just didn’t know how important it is to ceruleans,” Stravers said.
In May and June of this year, Stravers documented 192 active cerulean territories within the unit.
“Some bird people are going to have trouble believing that number,” he said.
In 2000, the Audubon Society petitioned the U.S. Fish and Wildlife Service to list the cerulean warbler as a threatened species, citing concerns over loss and fragmentation of habitat.
In rejecting that request, the service in 2006 estimated the population at 400,000 birds declining at an annual rate of 3 percent.
“We’ve lost 70 percent of the population in the last 40 years,” said Bruce Ehresman, a biologist with the DNR’s Wildlife Diversity Program.
Stravers — known by his bird-loving friends as "Hawk" for his intensive research of red-shouldered hawks and to his grandchildren as "Hawk Daddy" — said he went “Hawk Daddy nuts” this year in his cerulean research.
From May 5 through the end of June, the period during which male ceruleans sing on territory, Stravers said he was in the woods every morning and evening.
“I started going beyond my standard search points, into the deepest canyons with the biggest trees, the hardest places to get to,” he said. “Where I thought there were four birds, I found there were a dozen.”
Named for the color of its plumage, the secretive neotropical migrant resides in the canopy of tall trees, where it becomes virtually invisible against the backdrop of the cerulean sky. Few Iowans have ever seen one.
“They occupy the extreme highest region of the canopy, 60 to 80 feet off the ground,” said the DNR's Ehresman, who was fortunate enough to see an adult feeding young during an outing last year with Stravers.
Even Stravers, who lives among them for two months each year, relies almost exclusively on his ears to identify their territories.
The cerulean’s buzzy trill is often described as a series of zee sounds that accelerate and rise in pitch at the end.
Stravers translates it as, “This is my territory. This is my territory.”
“Jon has a sixth sense. He just knows where to look for them,” Ehresman said.
Stravers said it’s not quite a sixth sense.
“My brain has developed a search image for their song. I’ll be going about my business, not really listening for a cerulean warbler, and I’ll realize I just heard the trill,” he said.
At 64, Stravers said his knees are gimpy and his vision is not as sharp as it once was, but his hearing is as keen as ever.
To be named a Globally Important Bird Area, a state area must meet strict requirements backed by research indicating the site’s importance to imperiled birds, Harr explained.Formal recognition is planned during the HawkWatch event, Oct. 5, at Effigy Mounds National Monument.