Each May, some residents of the Cincinnati suburbs look up to see Cheryl Rozema Dykstra ’88 about 50 feet above the ground, in mature trees on their lots. They know she’s looking for chicks in the nests of red-shouldered hawks.
For 15 years, Dykstra and her team of volunteer researchers have been conducting the only detailed study of a suburban population of red-shouldered hawks in eastern North America. Their findings are expanding knowledge of and appreciation for a remarkable bird, not only in scientific circles, but in Cincinnati’s residential circles as well.
Dykstra began her study of raptors with bald eagles in graduate school. After completing her PhD, she moved with her husband, Robert Richard Dykstra ’88, to Cincinnati to conduct a study for the U.S. Environmental Protection Agency on whether red-shouldered hawks give clues about the area’s water quality.
That study ended in 1999, but her interest in the species didn’t.
“Two volunteers and I wanted to keep going,” she said, “because changes in species’ populations due to environmental insults are only detected by long-term studies.”
While also working as a wildlife consultant and editor-in-chief of a scientific journal, Dykstra has been investigating how red-shouldered hawks co-exist with humans. In particular, her team is looking at how successful suburban Cincinnati birds have been in reproducing.
“If something has gone wrong in the environment, one of the first things you’ll notice is that their eggs won’t hatch or they’ll have fewer young,” she said.
The team has found that even though development is shrinking their habitat, suburban red-shouldered hawks are fledging as many nestlings per active nest as their rural cousins.
“The only difference we found between the two populations is that suburban birds will nest closer to houses and roads. We even had one pair nest on the roof of a three-story apartment building four years in a row, successfully producing young every year. They’ve adapted quite well to humans.”
Still, the parent birds are not always happy to have Dykstra lifting chicks, however briefly, from their nests. They sometimes stoop or dive and, on about 5 percent of her climbs, hit her. She wears a helmet.
The chicks, however, are “very mellow,” according to Dykstra. So mellow that after she has banded and measured them, she puts them in the hands of landowners and their delighted children.
“We make quite an effort to get people out to see the nests and nestlings,” she said. “Education is the first step to conservation.”
Dykstra’s team is studying whether certain measurements they’ve taken on the nestlings indicate their sex and also how far those banded nestlings, once they’ve grown to reproductive age, disperse to build their own nests.
“There’s surprisingly little known about raptor behavior in suburbs,” she said, “and the more we learn, the more questions come up.”
For example, her team recently discovered that 80 percent of the nests they visited were decorated with black cherry sprigs, though only 5 percent of trees in the nesting area are black cherry. Now they’re asking, is it because the crushed leaves produce hydrogen cyanide, a natural pest repellant?
“Red-shouldered hawks are remarkable birds and, I feel, glorifying to God,” Dykstra said. “At Calvin I came to appreciate that God’s kingdom plan involves restoration and redemption of the whole creation, not just people. My hope is that our research can, in some small way, help with that.”
Learn more about Dykstra’s work