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Prairie still for the birds

Group tracking nests’ success amid bison at preserve

FRANKLIN GROVE – Birds can be as fickle as their nests are fragile. So one might think a three-quarter-ton beast would be detrimental to our feathered friends.

Not so. At least not yet. Heather Herakovich, in her third summer studying nests at Nachusa Grasslands, has seen a steady thriving of nests in the prairie that about 80 bison – not including new calves – call home.

There’s a simple requisite for a nest to be successful: that the eggs hatch, and the chicks leave the nest. About a third of nests make it. The other two-thirds are likely doomed by predators, or by parasitic birds laying eggs in others’ nests, at which point, many parent birds abandon their offspring.

Thanks to funding from Friends of Nachusa, the DuPage Birding Club, the Illinois Association for Environmental Professionals, and Northern Illinois University, where she’s working on her doctorate, Herakovich, 26, of DeKalb, has honed in on aviary tendencies.

Her first year, she worked alone, then got to add an intern or two a year ago. This year, she welcomed Heather Dauen, a 2004 Sterling High School graduate, to the team. They’ve found 42 nests this year, for a 3-year total of 138 so far.

The 10 species are lark sparrow, field sparrow, dickcissel, red-winged blackbird, eastern meadowlark, morning dove, grasshopper sparrow, song sparrow, common yellowthroat, and brown thrasher.

The cowbirds don’t build their own nests, they only squat in others’. Call them lazy, but there’s something to be said for playing the system.

“Well, it’s working for them, and they’re not the only species that does it,” Herakovich said.

Every few days, the group examines bird nests’ composition in three units within the bison’s fenced-in space, and three more outside – a classic variable-constant setup.

Other NIU students have dialed in on composition of amphibians, snakes, ground beetles and other populations.

Much like Nachusa stewards, who helped bring the bison back to the Prairie State about 2 years ago to restore native species, the students think the bison will improve and change the prairie for the good of the species they’re researching.

“But we don’t yet know whether it will work that way,” Herakovich admitted. “I haven’t found a difference with the bison being in there, in terms of nest density and nest success, the probability of the nest producing fledglings, and brown-headed cowbird parasitism.”

She’d hypothesized that because the cowbirds tend to flock around livestock, their presence would increase. Not so. Not yet. Again, it’s early in the game. Much like many native plant species that take several years to bloom, nature often plays a long game.

“If there’s going to be a discernible change, I think it will be later on,” Herakovich said.

Nachusa is unique in that it’s one of the first restored prairies (planted by humans) to bring in bison, whereas out West, bison predominantly roam remnant prairie, she noted.

She wonders whether the successful nests’ fledglings return to Nachusa as adults – a phenomenon called breeding-site philopatry – after migration, but to glean that, the birds would need to banded or tagged with GPS. That’s the sort of research that would require more than, say, three interns.

Her chief mission while teaching her interns is to send them away with more knowledge, including the ability to identify birds and their song.

So Herakovich gushes about Dauen’s plan to plant and run an educational prairie alongside her Sterling home.

“It’s super-cool to have people out there who are just as passionate about the research, but have not been in the field, and to see them fall in love with what we’re doing, like she has,” Herakovich said.

“I think she’s got a great idea, and it’s so important to teach the younger generation that this is still considered the Prairie State.”

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