Menu

A savannah sparrow takes respite on a fence post in a Wisconsin pasture.

At first, all you see is the three-foot-long milk snake, a compact spiral that fills the center of the video screen. Then Daniel Schneider BS’07 points out a tiny beak, nearly obscured by the snake’s banded markings. It’s all that’s visible of a fledgling sparrow being crushed in the tightening coils.

Schneider has watched a lot of this kind of mayhem. As part of a research team led by CALS wildlife ecologist Christine Ribic, he has accumulated hundreds of hours of video spying on the nests of grassland birds. He’s seen chicks and eggs devoured by snakes, skunks and deer, leaving no doubt life is tough for the birds that nest in Wisconsin’s tall-grass prairies. It doesn’t help that those prairies are small and fragmented, putting the birds’ nests in reach of woodland predators.

But the footage also shows that protecting grassland birds isn’t as simple as protecting grassland. Ribic’s team put cameras on nests in six grassy sites—three near tree lines and three in locations where trees had been removed to create more open habitat. While clearing trees did tend to increase nesting of some bird species, it also cleared the way for new predators. Chief among them: the grass-dwelling ground squirrel, which was the culprit in up to 75 percent of nest raids where trees had been removed.

That doesn’t necessarily mean that removing trees won’t work in the long run. Ribic’s team will return to the sites in five years to see if the impacts on both birds and ground squirrels were short-term or permanent. But the findings are a reminder that there’s no such thing as a small change in a natural system.

“When you create new grassland in an area where grassland is limited, it’s not just birds that will want to live there,” Ribic says. “Everything else that lives in grasslands, including predators, is going to take advantage of the new habitat. The whole system changes. You have to think bigger.”