Like many large birds of prey, fish hawks, also known as osprey, were once plentiful across much of the United States. Unfortunately, as with many large birds of prey, the osprey population was decimated by development, hunting and pesticides. In South Dakota, where the birds nested and hunted along the Missouri River, the osprey is listed as a threatened species. But now, wildlife officials are working to bring the osprey back to the region.
It's said that the stretch of Missouri River just outside of Vermillion looks much the same as it did two centuries ago, when Lewis and Clark began their journey of exploration across the American West. The cold, churning water teems with a variety of fish and wildlife as it winds through the rustic terrain.
But it's not all the same… About 50 kilometers upriver, the Gavins Point Dam near Yankton betrays man's efforts to control the course of the Missouri for flood control and recreation. This facility and other developments helped eradicate some of the animal species Lewis and Clark's team saw along the river, including the osprey.
"It hasn't nested in this part of the state in over a hundred years," said David Swanson, a biology professor at the University of South Dakota. He says it's not uncommon to see osprey along the Missouri River during the migration season. They typically move from Canada to southern Mexico and Central America during the winter and travel back through in April.
He says all signs indicate that the osprey was a permanent resident in the area before settlers moved in and began farming.
"There were reports in the late 1800s from the summers; we know they were nesting here," he said. "But because of the changes in the practices that had gone on, in terms of the DDT, or something that really reduced their populations down."
Throughout the 19th century, settlers shot and killed scores of osprey. Agricultural use of the pesticide DDT which was banned in the 1970s polluted area waterways, tainting the fish the birds fed on. The chemical also caused their eggs to develop thinner shells, which often broke before they could hatch.
This summer, the state Game Fish and Parks Department began efforts to reintroduce osprey in this area. Conservation Officer Chad Morrow says the stretch of river between Gavins Point Dam and Vermillion is ideal for the project.
"The habitat down here along the Missouri River, being fairly undeveloped is very conducive to osprey's natural habitat, and that's why they decided to do their re-introduction project along the Clay and Yankton County line," he said.
Mr. Morrow adds that since the large birds are classified as a threatened species in South Dakota, state officials were obligated to try to re-establish them.
So, this summer, nine osprey chicks from a breeding program in Minnesota were brought to South Dakota. They were held and fed in hack boxes - artificial nests placed in towers to simulate conditions under which they would live in the wild. Five chicks were placed near the dam, the other four at Clay County Park near Vermillion. Out of the nine, six survived. Officer Morrow says West Nile Virus probably killed the rest.
"All the birds of prey are very susceptible to West Nile," he said. "We did have three of the birds in the hack boxes die - one was confirmed to have died of West Nile, and the other two are presumed to be West Nile also."
Despite the setback, South Dakota wildlife officials are committed to seeing the process through. And some local residents have taken notice.
Terry Robertson owns a tract of land about halfway between Yankton and Vermillion. A four-hectare pond on his property provides a reliable water source for deer and other wildlife. He says, earlier this year, he and his wife saw one of the osprey chicks at the pond.
"And at first I thought it was a hawk, because I was far away. But as we came closer to it I knew what it was," he said. "We got within 10 or 15 yards of it, and it never flew. It just kept watching the water, like it was stalking for fish or something."
Mr. Robertson says he immediately called his son, a doctorate student in animal biology at the University of North Carolina, to describe the bird and confirm that he had, indeed, seen an osprey.
"And he said, take a camera next time! Get a picture, get a picture. And so we took the camera with us and within the next week while we were walking we saw it out there again," he said.
Officials involved with the re-introduction effort encourage other residents to report sightings of the birds. The six surviving chicks have left the area and now on their way to Mexico.
The 66 percent survival rate is a pretty good result for the Game Fish and Parks project. But USD professor Dave Swanson says it's still too early to tell whether re-introduction efforts will succeed.
"The idea is that it'll be a self-sustaining population," he said. "They'll come back and produce young, and the young will come back and they'll increase in numbers along the river and keep breeding there so that the population sustains itself."
The biologist says osprey often return to familiar breeding areas. So the return of the chicks in the spring will be one indication that osprey are able to thrive on the Missouri.
