A new study of the migratory behavior of a rare shorebird, funded by the Bureau of Ocean Energy Management, suggests that the impact of a growing number of turbines will not be benign.
The rufa subspecies of the red knot, a bulky chestnut shorebird that breeds in Arctic Canada and winters along a wide swath of coastal habitat from the Southeast to the southern tip
of South America, is a federally-threatened bird whose
populations have declined precipitously in recent decades. During the spring
and fall, they migrate over the Atlantic, and some stop to refuel at select
sites along the Eastern Seaboard.
|Red knot (stock)|
The birds’ migratory route offshore – as well as their altitude, timing and preferred environmental conditions – was unknown until a group of researchers from the U.S. Fish and Wildlife Service and partners in Canada, New England and New Jersey placed nanotags on 388 knots in the fall of 2016. When the birds flew within detection range of one of 35 radio towers from Cape Cod to Virginia – including four in Rhode Island – their location, altitude and direction was recorded.
According to Pam Loring, the Rhode Island-based Fish and Wildlife Service biologist who led the study, the results indicated that red knots migrate south in fall in two distinct waves.
“Those that came through during early fall went straight southeast over the open Atlantic Ocean and were likely heading nonstop to South America,” she said. Most of those birds probably traveled far to the east of any of the areas targeted for wind energy installations, so those early migrants are unlikely to be affected by wind turbines in U.S. waters the future.
“The second wave came through in November and went more in a southwest direction,” Loring said. “Birds from Cape Cod cut across the mid-Atlantic Bight and arrived in the mid-Atlantic coastal region from New Jersey to Virginia.” Those birds intersected with a large area leased for wind energy off New Jersey.
Most of the birds in the second wave were recorded flying less than 200 meters high, placing them at an altitude in which they would risk colliding with wind turbine blades. Loring said, however, that there were “high uncertainties” in the data about the precise altitude at which the birds were flying.
Still, in a report she wrote for the Bureau of Ocean Energy Management, Loring noted that the study’s elevation results place “the short-distance wintering population at higher level of exposure to potential effects from offshore wind energy development.”
Among the other findings of the study, Loring said that the birds typically departed for migration just prior to sunset when skies were clear and they had a tailwind.
“Using the dates, winds and other conditions, we can predict when their movements would occur,” she said. That means that one option for future management of offshore wind farms is to curtail turbine operations during the time periods when red knot migration is most likely to occur. That strategy is frequently used in the West to protect migrating hawks and eagles from collisions with land-based wind turbines.
A similar study Loring is co-leading with University of Rhode Island ornithologist Peter Paton is examining the offshore movement patterns of piping plovers and roseate terns, two birds on the federal endangered species list that breed in coastal southern New England and probably migrate offshore through areas designated for offshore wind development. A report of the results of that study, which included tagging birds on Rhode Island beaches, is due later this winter.
In addition, Paton is leading a study of the movement of various species of birds and bats around the Block Island Wind Farm, using a tracking antenna installed on one of the turbines.
“There are several thousand tags out there on a wide variety of bird species being studied by other researchers,” Loring said. “So we’ll be looking at data from whatever species happen to come through.”