Anoka County oaks may hold clues to saving redheaded woodpeckers

Elena West and her team stood in the grass beneath a towering dead oak tree and hoisted a camera far above their heads.

As they watched from below, the monitor showed two young redheaded woodpeckers, alive and well, nestling together inside a small cavity high up in the oak. The birds were old enough that they would be ready to take wing and leave the nest at any moment, said West, a researcher with the University of Minnesota.

She and her team of researchers were at the small stand of oaks in Anoka County because that sight — a successful hatch and fledging of a pair of redheaded woodpeckers — is so increasingly rare it can only be seen now in a handful of places in Minnesota.

Redheaded woodpeckers — friendly, busy birds once familiar to anyone growing up in Minnesota — are disappearing from the state. They have lost about 95% of their population in recent years and seem to be vanishing just about everywhere — except for a small oak savanna in northern Anoka County called Cedar Creek. There the birds have been able to survive in relatively stable numbers over the past decade, with between 70 and 100 adults nesting among the oaks every year.

Now scientists with the U and the Audubon Society are studying the little savanna to find out why it has become a refuge for the woodpeckers and whether it holds any lessons about habitat that might be used to rescue them elsewhere.

"There's just so much we still don't know," West said.

Small, lively and beautiful, the woodpeckers have a devoted following among bird-watchers. But even though they were once ubiquitous across the Midwest, ornithologists know very little about them.

Sometimes they migrate for winter, but nobody really knows where they go or why. They seem to nest almost exclusively inside dead oak trees, burrowing and cleaning out cavities for shelter. The birds don't seem to survive long in either dense forests or open prairies. Instead they need the blend of those two habitats that savannas provide.

It's that reliance on savannas that may be their death knell.

Scientists believe that oak savannas — smatterings of the big, gnarled trees spread out over vast acres of rolling prairie grasses and wildflowers — once covered much of southern Minnesota. But they were easy to clear and offered abundant wood supplies, making them extremely attractive to frontier settlers, and they were typically among the first places developed and farmed as the young state's population grew.

Minnesota's oak savannas have now almost entirely been cleared, turned into cropland or simply lost, leaving less than 1% intact, according to the Minnesota Department of Natural Resources (DNR).

As the oak savannas disappeared, so have the redheaded woodpeckers, West said.

Any long-term rescue needs to start with restoring that habitat, she said.

The U and the Audubon Chapter of Minneapolis received nearly $200,000 from the Legislature this spring to use their findings to guide how Minnesota might restore large swaths of land, especially in state parks. In recent years, the DNR has been leading a push to restore oak savannas — to save not just woodpeckers but also bumblebees, butterflies and other pollinators whose populations are threatened.

Winged engineers

Cedar Creek is one of the last corners of oak savanna left in Minnesota. The 5,500-acre property is owned by the U, which keeps it as a science reserve with dozens of projects and decadeslong studies underway at any one time.

Over the past several years, researchers have grown more interested in the redheaded woodpeckers because they may play a crucial role in the larger ecosystem. The birds act like engineers, digging out holes that become shelter not just for them, but also for various species of squirrels, birds and other woodpeckers, West said.

They can be clever, using tree stumps as platforms and for leverage to crack open acorns. They store nuts for the winter, like hibernating squirrels, and have been spotted stuffing away insects inside tree bark for a meal later on.

To save them, scientists need to learn more about where they go when they migrate, West said.

This summer, she and a handful of research technicians and citizen volunteers have been capturing and tagging a few dozen adult and juvenile woodpeckers. They attached tiny GPS and radio transmitters to the birds with custom-made straps that slip over their wings like backpacks. The birds will be recaptured in the spring, allowing researchers to download exactly where they traveled through the winter and get a better sense of what they eat and where they can survive.

"We have no sense of how far they go," West said. "We know they're not going all the way to South America, but it could be Illinois or Missouri. We really don't understand how they make those decisions."

Researchers at Cedar Creek also hope to learn what triggers their migration, said Siah St. Clair, a member of the Audubon Chapter of Minneapolis board of directors. It's possible that the birds decide to migrate in search of food when acorns and other nuts are particularly scarce, or when winter temperatures drop, or if the population has grown too much and they need space, St. Clair said.

"We have so many guesses but need evidence to start backing them up," he said.

Belly of a bullsnake

Research into the woodpeckers is so new that scientists are still learning what their predators are.

Sarah Stewart, a research technician at the science reserve, recently followed a transmitter attached to a young fledgling — and discovered the bird inside the belly of a bullsnake. It was the first evidence that snakes are among their predators. A trail camera set up by St. Clair showed a pair of adult woodpeckers trying to fight off a flying squirrel that was apparently going after their eggs.

"We're learning with everything we do," he said.

What may make Cedar Creek so special for redheaded woodpeckers, West said, is that the property was one of the first in the country to start a regular prescribed burn program, which clears away the brambles, weeds and weaker trees that would otherwise strangle young oaks. The savanna ecosystem depends on fire, West said. Without regular burning, the grass and underbrush stockpiles, building up enough fuel that when a wildfire does breakout it becomes intense enough to take down large and ancient trees.

The early signs from Cedar Creek suggest that woodpeckers can live in relatively cramped places, which is a good sign for their future, West said.

It would be progress, she said, "if we can just find out things like if there's a number of dead trees that should be kept, or the kinds of plants you'd need to bring these insects or other food sources."

In her research, West has been reading old journals and talking to farmers from decades ago, who remember times when hundreds of the woodpeckers would gather on a single cherry tree. She said she's hopeful that a species that was once so abundant will prove resilient.

Greg Stanley • 612-673-4882