His granddaughter calls him “Hawk Daddy” and he moonlights as a folk musician. He recognizes bird calls so precisely that he knows — by nickname — who is making them.

Meet Driftless Area bird researcher Jon Stravers, a free-spirited zealot who spends countless days on the Mississippi River and its backwaters immersing himself in observation and thought.

He has been tracking red-shouldered hawks for more than 30 years and his data on cerulean warblers in the region helped certify Iowa’s first globally important bird area.

Stravers’ research home is the woodsy, watery region where Minnesota’s southeast corner converges amid blufflands with Iowa and Wisconsin. His keen insights as a self-described “river dog” helped Minnesota DNR win an active $1.55 million grant to restore lost fish habitat and patches of floodplain forest between the tiny river towns of Reno and Brownsville.

Over the next several years, the so-called Reno Bottoms project will dredge sediment from a backwater bay to improve fishing. In turn, crews will dump the silt on an island now covered by invasive Reed canary grass. The transfer will enable the planting of native tree species that have been lost to ever-rising water. Funding came from the Legislature as recommended by the Lessard-Sams Outdoor Heritage Council.

According to Hawk Daddy and others, changes to hydrology are robbing the region of its rich diversity of plant life and wildlife. The Reno Bottoms project will benefit bluegill, crappie and bass populations within a fishing area of upper Pool 9. Shore birds, amphibians and other critters also will benefit from the enhancement.

“He’s a phenomenal resource,” said Dan Dieterman, Mississippi River habitat specialist for the Minnesota DNR. “His love of birds and the places they live is truly infectious.”

Thunderbird heart

Dieterman recalled a chance encounter with Stravers at the back end of a hidden slough in the middle of Reno Bottoms. When the two stumbled into each other, Stravers was listening for birds. They were both annoyed by the disturbance of seeing someone else until they realized they knew each other.

“I think we were both surprised to see someone else in such a remote location,” Dieterman said.

Stravers, a Vietnam War veteran who sailed into the Mekong Delta on the morning he turned 21 years old, said his sojourns on the river aboard his 17-foot, flat-bottomed boat aren’t always for work. All it takes is a good moonrise to lure him to the water, or any number of inner feelings.

Stravers lost his son, Jon-Jon, to a motor vehicle crash 12 years ago. Jon-Jon was a 33-year-old artist who shared his father’s passions for ornithology and making music. The young man designed an image of a raptor in the likeness of a sacred, Native American thunderbird. It’s displayed on Stravers’ boat and he talks openly about his spiritual connection to Jon-Jon and the mystical thunderbird of darkness and light.

From mid-March until July, Stravers ventures out of his home in McGregor, Iowa, twice a day to survey birds on the river and in the surrounding 400-foot hills. On his milk runs of nesting sites he checks for potential vacancies or new tenants — making a note at each place.

“From mid-March to July I’m a fool. I’m obsessed,” he said.

In the fall, he tracks the migration of raptors, and various agencies still rely on his expertise of trapping the birds in nets and banding them.

Critical diversity

Like other scientists, Stravers has observed the prolonged inundation of trees on flooded river islands in the Driftless Area. In some places, dead trees stretch for miles, with their lower trunks covered by water. The problem has grown from years of abnormally high rainfall coupled with the runoff of agricultural soils. The silt impounds itself in slower, wider stretches of the river, raising the river’s floor.

Stravers has documented how the loss of swamp white oaks, black walnut trees, hackberry trees, basswoods and other native species have coincided with the movement or departure of red-shouldered hawks, cerulean warblers and other birds.

The diverse floodplain forests of old are being replaced by islands of Reed canary grass and solid stands of silver maple trees. Stravers believes certain birds need the open canopies provided by the normal mishmash of native trees.

“We’ve really lost a lot of species diversity within the floodplain forest,” he said.

He documented the departure of four nesting pairs of red-shouldered hawks from one 3½-mile stretch of the river over five years. He also has watched other birds vacate patches of forest that lose their diversity. For cerulean warblers and prothonotary warblers to migrate to the Driftless Area from their tropical winter homes, they need old-school, bio­diverse floodplain forests, his research has found.

In the field, Stravers relies mostly on sounds to fill out survey data. After so many years enmeshed with his study subjects, his brain has developed a “built-in search engine” for bird calls. For instance, the mono-pitched, buzzy call of the tiny blue cerulean stops him in his tracks even when he is paying attention to something else.

All in a name

He deciphered seasonal dialects of red-shouldered hawks and nicknamed his subjects with monikers like Snake Bite, Rufus, Charismatic and Twimbly. He said it was Jon-Jon who persuaded him to lose his tunnel vision for the hawks and diversify into the study of warblers, cedar waxwings and other birds.

“I’m so glad he did that,” Stravers said. “It was the student becoming the teacher.”

Stravers has worked for years with the Audubon Society and currently contracts with other wildlife groups, including the U.S. Fish and Wildlife Service. Besides his ongoing historical inventory of nesting birds in Navigation Pools 9 and 10 on the Mississippi River, he has assisted federal researchers in mapping the change to tree stands in the region.

His musical wanderings include performances with a band called Big Blue Sky. The group’s latest recording is called “Bird Dance … Dancing the Dream Awake.” He also has his fourth book in the offing. He’s calling it “Chasing the Bird Dream.”