Researchers have found that breeding ospreys have increased from 11 pairs in 2010 to 14 in 2011, 18 in 2012 and 26 in 2013.
Despite low productivity in 2013, the overall upward trend is positive, said David Rimmer, Greenbelt director of stewardship, in the report.
“Greenbelt is expecting the nesting osprey population in Essex County to continue to expand in 2014,” wrote Rimmer.
Rimmer told the Salem News that ospreys, which should be returning to the area in late March, are “an indictor of the health of a coastal ecosystem.”
In his report, Rimmer said osprey populations decreased dramatically between the 1950s an 1970s because of “unregulated use of pesticides, which weakened osprey eggshells and caused nesting failure and poor production.”
US laws in the 1970s regulated pesticide use and researchers began seeing the osprey numbers rebound across North America.
Ospreys had been spotted in Essex County for decades, but it wasn’t until the 1980s when the first confirmed pair of nesting osprey were observed on a man-made platform in Essex. The nesting birds have been gradually increasing over the past three decades.
32 nests in 2013
Greenbelt observed 32 nests in Essex County in 2013. Researchers found 26 “active” pairs, which includes a nest in Danvers, two in Marblehead and one in Salem.
Rimmer told the Salem News that the ospreys nested on a large transmission tower along the Danvers River and boaters’ navigational day markers in Salem and Marblehead.
Danvers and Marblehead both had “successful” nests. There were 10 “successful” nests in Essex County, according to Greenbelt.
Of the 26 active pairs, researchers counted 21 fledglings.
“The overall productivity rate was 0.88 fledglings per active breeding pairs that laid eggs, which research suggests is slightly below the productivity level believed necessary long-term to maintain and/or grow an osprey population,” according to the report.
As part of the research, Greenbelt also placed US Fish and Wildlife Service aluminum leg bands on 13 flightless chicks and placed satellite transmitters on two of the banned young “after they fledged as part of a larger study of osprey migration behavior." The two left Essex County in September. One died in Pennsylvania in late September, but the other is alive on the north coast of Venezuela.
The Greenbelt is encouraged by the report and plans to expand its osprey Program this year.
“Greenbelt played an important role in osprey conservation in Essex County in 2013 by ensuring nest sites/structures were stable and well monitored by volunteers and staff, by expanding public outreach and education, and by conducting research. Greenbelt plans to continue with and expand the osprey Program in 2014.”