by Stephanie Smith
March 24, 2017
An osprey carries away a pipefish it snatched from Knapps Narrows near Tilghman Island, Maryland, on September 1, 2015. Also known as fish hawks, ospreys are harbingers of spring in the Chesapeake Bay region. The raptors begin arriving in early March and remain along the estuary’s shorelines, rivers and marshes through late summer.
In the mid-twentieth century, the widespread use of pesticides and industrial chemicals led to the near-collapse of the Chesapeake’s osprey populations. The pesticide dichloro-diphenyl-trichloroethane—known commonly as DDT—was causing female ospreys to lay eggs so fragile that they cracked under the parents’ weight. By 1972, when DDT was banned in the United States, there were fewer than 1,500 pairs of osprey in the Chesapeake Bay region.
High levels of polychlorinated biphenyls, or PCBs, have also been found in the eggs and chicks of ospreys that nest along the Bay. These industrial chemicals act as flame retardants and have been used in the production of inks, adhesives, sealants and caulk. While PCBs have not been produced in the United States since their ban in 1977, their ability to persist in the environment means the chemicals continue to be widespread in the region—and can expose ospreys to potentially harmful residue.
Despite the threat of these long-lasting pollutants, recent research has shown that ospreys are thriving in the Chesapeake Bay. As many as 10,000 pairs of the resilient raptors breed in the region—close to one-quarter of the osprey population in the contiguous United States.
As part of the Chesapeake Bay Watershed Agreement, the Chesapeake Bay Program’s Toxic Contaminants Workgroup is working to reduce the impacts that chemical contaminants have on the Bay and its rivers—and the wildlife and people that depend on them.