WSB: What if you build it and the cranes don’t come?

By David Frey

State-threatened Florida sandhill cranes are losing their nesting habitat to development throughout the state. Credit: Tim Dellinger/Florida Fish and Wildlife Commission

As urban development eats away at habitat for the state-threatened Florida sandhill crane, biologists were hoping they could improve the birds’ outlook by improving conditions for them on state lands.

Using prescribed fire and machinery to thin out dense stands of saw palmetto and shrubs, researchers believed they could transform the landscape into one with the kind of conditions the cranes should take to.

“It’s one of those things where, if you build it they will come—we were hoping,” said Tim Dellinger, research scientist with the Florida Fish and Wildlife Commission. “But during our time frame, they did not.”

But the cranes never showed up, leaving researchers stumped.

“I’m not sure why the birds didn’t come, but they didn’t come,” said Dellinger, who led the study published in the Wildlife Society Bulletin.

Sandhill cranes (Antigone canadensis) are famous for migrating in flocks of thousands across North America. But the Florida sandhill crane (A.c. pratensis) is just one of three nonmigratory subspecies, occupying wetlands between southern Georgia and the Everglades. Biologists aren’t sure how many there are—likely more than 6,000—and ironically, their numbers are increasing even as their nesting habitats disappear. Instead of using natural areas, the cranes seem to be moving into suburban areas, Dellinger said, making use of backyard birdfeeders.

That’s not so healthy for the cranes, he said, but it’s great news for the neighbors who love them—and often even name them.

“It’s a really high-profile species,” Dellinger said. “A lot of people really love the cranes down here.”

Between 1974 and 2003, over 40% of their habitat was lost to development and other land use changes, researchers found. By 2016, less than 16,000 square kilometers of their preferred habitat remained, mostly on private lands that may also be at risk of development.

Florida’s state natural areas aren’t usually managed with sandhill cranes in mind, Dellinger said, but if they were, it could provide more areas for the birds to nest. Historically, they used shallow marshes on Florida’s dry prairie. Those landscapes have since become overgrown with sharp saw palmetto and shrubs that make it hard for cranes to pass.

In an experiment from 2014 to 2016, his team deployed crews to native dry prairie at Three Lakes Wildlife Management Area and to nonnative pasture at an adjacent ranch in Kenansville, Florida. The crews used both prescribed fire and a mechanical thinning process known as roller chopping to clear out the scrub and make the landscapes usable by cranes again.

The treatments seemed to work. Shrub densities decreased more than 13%. Grass densities increased by 15%, making them similar to the pastures where the birds often appear to nest.

“We really thought this was a no-brainer,” Dellinger said.

But after nearly 300 hours of flight time looking out airplane windows for signs of breeding activity, researchers saw no sign of nest density increasing. Maybe weather was the problem, Dellinger said. Unusually heavy rain delayed the roller chopping, forcing contractors to split it up between two years. Or, he said, “it may just take a long time for the birds to come and start using these areas.”

Dellinger is hopeful the birds will take to them eventually. In the meantime, his research is focusing on how they are making use of suburban resources instead.

“We’re just hoping our work’s beneficial and it contributes to keeping the cranes around,” he said.

This article features research that was published in a TWS peer-reviewed journal. Individual online access to all TWS journal articles is a benefit of membership. Join TWS now to read the latest in wildlife research.

David Frey is managing editor at The Wildlife Society. Contact him at dfrey@wildlife.org with any questions or comments about his article. Read more of David's articles here.

You can follow him on Twitter at @davidmfrey.


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