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Ospreys and the Michigan Wildlife Action Plan.

Ospreys (Pandion baliaetus) were once found throughout Michigan but, along with several other top avian predators, their population was severely depleted in the mid-20th century due to the effects of DDT, PCBs, and other pesticides that caused egg shell thinning. In Michigan, the number of occupied nests declined to just over 60, primarily in the Upper Peninsula. After the use of these chemicals ended in the 1970s, osprey populations across the continent began to rebound. Surveys in 1988 and 2003 located 167 and 220 Michigan pairs, respectively, but again they were restricted almost completely to the Upper Peninsula and northern Lower Peninsula.

The osprey is categorized by Michigan as a "threatened" species and is recognized in Michigan's Wildlife Action Plan as a species of great conservation need. One goal for the long-term sustainability of Michigan's osprey population has been to expand its range back into the southern parts of the state. To address this goal, the Michigan Department of Natural Resources (DNR), with several conservation partners, initiated an osprey reintroduction program in 1998.


After fledging, young ospreys from Michigan fly to Florida and South America. In April of their second or third year, ospreys often return and establish nests in the area where they learned to fly. Biologists take advantage of this behavior by removing 4-week-old chicks from their home nest and raising them in a different location in the wild, to which we hope the birds will return as adults. Adult ospreys continue to migrate annually between their selected northern breeding area and southern wintering grounds.

The transplanted osprey chicks are placed in a large, enclosed "hacking box" where they are provided fresh fish, water, and plenty of room to exercise their wings. As they grow and mature, the hack box is opened and chicks are allowed to leave. Some fly immediately, while others take time to further strengthen their wings. Fish are provided for fledged chicks until they migrate south, by which time the fledglings have learned to catch fish on their own.

The goal of Michigan's osprey reintroduction program is 30 established pairs in the southern Lower Peninsula by 2020. However, due to the long delay between fledging and the return of adult ospreys, similar programs in other states have required 10 years of hacking before seeing real success.

Initially, this program was supported through Michigan's Nongame Fish and Wildlife Fund with matching contributions from partners. But in 2000, the primary source of donations to this Fund (a check-off on the state income tax form) was removed. The reintroduction program would likely have ended or been severely reduced without the infusion of federal funds through the Wildlife Conservation and Restoration and State Wildlife Grants programs. Instead, reintroduction efforts were able to continue.

The benefits of this program have been greater than we expected. So far, 59 osprey chicks have been successfully reared and released. During the 2006 breeding season, 13 osprey pairs were nesting in Michigan's southern Lower Peninsula. They include identified graduates of Michigan's hacking program and others that may or may not have been hacked in Michigan. Ospreys released in southern Michigan have also been reported in other Midwestern states. Through this program, the DNR has formed new partnerships with Michigan bird researchers, the Detroit Zoo, Huron-Clinton Metroparks, DTE Energy, private landowners, and numerous volunteers.

The reintroduction project has produced new data on the natural history of ospreys in Michigan. For example, the success of chick translocations and the locations of active nests in southern Michigan indicate that ospreys may not be as sensitive to handling and disturbance as previously believed. In 2005, while monitoring osprey nests in northern Michigan to identify appropriate chicks for removal and hacking, biologists observed an unexpectedly high level of chick mortality. Although many factors may have contributed to the deaths, one collected chick carcass revealed West Nile virus as the cause. This virus has not been considered a significant threat to ospreys, but the susceptibility of osprey chicks may need to be reevaluated.

Recreational viewing of ospreys and a desire to assist in their conservation has led to the formation of a new organization, Osprey Watch of Southeast Michigan, an osprey festival, and a feature film documentary. Education and outreach associated with the reintroduction program may have improved the osprey identification skills of southern Michigan residents. Observers report that a few of the newly sighted osprey pairs in southern Michigan do not appear to have leg-bands, making it unlikely that these animals were released through the hacking program. Did these birds nest unnoticed in the area prior to the program, or are they new?


Michigan is considering the possibility of removing ospreys from the state's endangered species list. As part of a current review of the state's list, species experts on the Technical Advisory Committee for birds recommend deleting ospreys because of their increased numbers. The success of the reintroduction program was one of the reasons cited for this recommendation.

Once ospreys have been reestablished in southern Michigan, other threats to the population identified in the Wildlife Action Plan must be addressed. The Action Plan will continue to guide use of State Wildlife Grants funds and other funds that target the conservation of wildlife species and their habitats in Michigan.

Amy Clark Eagle, the Wildlife Action Plan Coordinator for the Michigan Department of Natural Resources--Wildlife, can be reached at P.O. Box 30444, Lansing, MI 48909- 7944; 517-373-1263 (phone), 517-373-6705 (fax).
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Author:Eagle, Amy Clark
Publication:Endangered Species Update
Geographic Code:1U3MI
Date:Oct 1, 2006
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