Asurvey by the Delaware-Otsego Audubon Society showed large numbers of golden eagles and bald eagles were moving north through Delaware County during March. Volunteers from the Franklin Mountain Hawk Watch counted migrating raptors from three sites south of Cannonsville Reservoir from March 5 to 14, and observed 66 bald eagles and 31 golden eagles migrating through a five-mile stretch in Hancock and Tompkins.

Audubon Society member Tom Salo of Burlington said volunteer hawk watchers expected to see golden eagles because they collaborated with people doing a study in Pennsylvania. Their work involved trapping the birds to put transmitters on them.

Salo said the GPS devices are accurate, so it was already known that tagged golden eagles had traveled along the corridor through Delaware County. But the bald eagle count was three times larger than what was recorded at five other notable northeast hawk watches during the same period. In addition, only one of those sites had more golden eagles than the

Delaware County sites. “The number of bald eagles was astounding,” Salo said Tuesday. “I personally watched one pair doing the foot grabbing and tumbling display, and then they landed on a branch and mated.”

Andy Mason of Jefferson, a longtime birder with the Delaware-Otsego Audubon Society, said there has always been an interest in where golden eagles migrate.

“It’s now pretty clear that there is a migration corridor there,” Mason said.

Salo said this study was the first time a migration count focused on the movement of the birds in spring. The raptor counts traditionally are done in the fall.

“Wind-power development is driving this project,” Salo said. “Nobody knew where the golden eagles were going, and for some reason, they are particularly susceptible to striking wind turbines.”

Another study of the migration corridor will be done next spring at three sites east of Otsego Lake, Salo said. The Upper Delaware River region is a major wintering site for bald eagles and occasionally, wintering golden eagles are also sighted.

Counters judge which birds are migrants, based on behaviors such as the type of flight, direction of movement, whether birds of different species are moving in the same way and if birds are engaged in foraging or territorial activity.

In addition to the birds judged as migrants, at least 17 bald and two golden eagles were observed but did not fit the criteria used to count migrating birds. Those bald eagles are likely local residents.

Scott VanArsdale, state Department of Environmental Conservation fish and wildlife technician, said the bald-eagle nesting population “has increased quite dramatically this year.” VanArsdale said there are now more than 200 nests statewide, compared to about 100 nests last year. VanArsdale added that there are no known golden-eagle nests east of the Mississippi River.