2008-06-11 / Sports

Outdoors 06/12/2008

Reintroducing Ospreys to Southern Michigan
AREAWIDE — Advances in chemical technology once were the undoing of ospreys in Michigan. Now, advancement in communication technology is proving to be a benefit to the Department of Natural Resources’ attempt to reintroduce the raptors in southern Michigan.
Once common in the Great Lakes region, osprey (Pandion haliaetus) populations were decimated as the use of DDT and other pesticides that caused thinning of the birds’ egg shells impacted the reproduction of the “fish hawks.”
After the use of DDT in Michigan was banned in 1969, the state’s osprey population began to increase slowly, but, by the late 1970s, nesting occurred only in the Upper Peninsula and northern Lower Peninsula.
State wildlife officials decided the opportunity to reestablish osprey in southern Michigan was ripe. A proposal to release osprey into southern Michigan was put together in the mid-1980s. The plan was based on a highly successful urban reintroduction project developed in Minnesota. However, the effort to reintroduce the endangered peregrine falcon began about the same time, so the osprey plan was put on the shelf.
“Once the peregrine program achieved success, the osprey proposal was resubmitted and funding support was approved through the Non-game Fish and Wildlife Trust Fund,” said Lori Sargent, the Wildlife Division’s osprey reintroduction coordinator.
The project also drew the attention of officials at Kensington Metropark and the Detroit Zoo, who expressed an interest in helping reestablish the osprey in southern Michigan.
The DNR initiated a program of relocating (also known as “hacking”) the raptors to southern Michigan in 1998, by removing chicks from active nests in northern Michigan and placing them in new locations.
Over a 10-year period, DNR staffers moved up to a dozen chicks a year to that part of the Maple River State Game Area in Gratiot County and Kensington Metropark in Oakland and Livingston counties. Now, there are at least 15 active nests in southern Michigan, many of them on cell phone towers across the state.
Reintroduction efforts have been so successful that the DNR does not plan any further hacking activities now. The goal is to have 30 active nests in southern Michigan by 2020.
During reintroduction efforts, DNR staffers removed male osprey chicks from their nests at four to five weeks of age, when the birds were old enough not to imprint on humans, but still several weeks away from flying. The birds were placed in hacking boxes, lined with twigs and grass, where they were fed rough fish until they were old enough to fly, then they were either physically removed from their boxes and placed atop them, or were allowed to fledge naturally. After release, feeding continued once daily to once every other day, by placing whole fish on top of the hack tower. Once the birds were observed fishing, feeding was reduced to every third day.
Prior to release, birds were marked in several ways — a green metal band on one leg (color and alpha-numeric code assigned by the Bird Banding Laboratory), a federal band on the other leg and a unique color of non-toxic spray paint applied to wings and underbody.
When autumn arrives, ospreys migrate south, anywhere from Florida to Central America and South America. Some remain in their wintering territories for several years while others migrate back the next season.
But they don’t mature and establish nests until they are three or four years old and generally establish nests within 50 miles of their hacking sites. In Michigan, adults arrive at nest sites in early April, laying two to four eggs in late April or early May. Most eggs hatch in the first half of June, and young fledge in late July or early August.
“The program is doing well,” Sargent said. “The birds are coming back. Every year there are new nests.”
Although the birds remain listed as a threatened species in Michigan, reproduction of hacked birds has been documented. Ospreys are more easily disturbed by human activity than other raptors, such as eagles, Sargent said.
For more information, visit Osprey Watch at www.owsem.org.
Courtesy Outreach Program, MI DNR

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