By Tom Dalton
---- — Ospreys are making a comeback in Essex County.
Once endangered, these large birds of prey are being spotted all over the North Shore in the spring and summer, with 26 nesting pairs confirmed last year, according to a report by the Essex County Greenbelt Association.
That’s a significant increase from 18 pairs reported the year before, 14 in 2011 and 11 in 2010.
Locally, nesting pairs of ospreys were seen in Salem, Marblehead and Danvers.
“The population has really expanded quickly and dramatically,” said Dave Rimmer, the Greenbelt director of stewardship and head of its osprey program.
“The birds that are nesting here are successfully raising their young, and those young are returning back here to nest.”
Ospreys feed almost exclusively on fish and nest near or in bodies of water. With wingspans up to 6 feet, they are often seen gliding low over water before diving feet-first and grasping fish in their talons.
Although ospreys can be found around the world today, their numbers declined a few decades ago, most likely a response to the wide use of pesticides.
Their comeback locally has been assisted by the Essex County Greenbelt, a private, nonprofit land conservancy.
To encourage the birds to nest here, Greenbelt has constructed more than a half-dozen wooden platforms, which make ideal homes for the ospreys’ large stick nests. Of course, the birds are known to seek out almost any tall structure, including the tops of buildings, telephone poles and electric transmission towers.
In Salem and Marblehead, ospreys nested last year on top of navigational day markers, which are used by boaters in open water. There were nests off the Salem power plant and off Forest River Park, Rimmer said.
There also was a nest on the Danvers River on a large transmission tower, according to Rimmer.
Rimmer credits an estimated 200 volunteer nest monitors and Greenbelt staffers with providing valuable reports last year on osprey activity.
“I’ve seen eight osprey flying at once off Forest River Park,” said Steve Saxe, a volunteer observer from Marblehead, who has photographed and documented nests in Salem and Marblehead.
The Greenbelt stirred up some excitement last year when it set up a webcam on a platform in a salt marsh next to its Essex headquarters, streaming live video. The nesting birds were viewed more than 60,000 times. The live video became a mini-drama, with three eggs producing only one chick, which died.
Two young ospreys were tagged last year with small transmitters to allow officials to follow their migration. The signal was lost from one bird, which presumably died, while the other is still on the move.
“It left from Gloucester and wound its way down the Atlantic coast and is now on the northern coastline of Venezuela,” Rimmer said.
The bird’s progress can be followed at the Greenbelt’s website at ecga.org.
The Greenbelt took on the osprey project not only because they are magnificent birds, but because they serve as a barometer of the environment.
“They are an indicator of the health of a coastal ecosystem,” Rimmer said.
The ospreys will start returning in late March.
Nesting osprey pairs in Essex County Marblehead 2 Salem 1 Danvers 1 Gloucester 1 Essex 4 Ipswich 6 Rowley 4 Newbury 2 Newburyport 1 Salisbury 4 2013 Total 26