Migratory sea birds, with tiny transmitters glued to their backs, are flying missions that will determine the collision risk between them and offshore wind turbines and show how they react to these structures.

Last summer Deepwater Wind installed a wildlife tracking station on the easternmost foundation platform at the Block Island Wind Farm, 3 miles off the coast of New Shoreham. The tracking station contains four antennas, plus a receiver that collects data on the migrating patterns of birds that scientists have previously tagged with tiny, high-frequency (VHF) transmitters, weighing about a gram each. These transmitters provide data on the tagged roseate terns, piping plovers, and common terns that fly within a 20-mile radius of the five turbines.

Five years ago researchers from the U.S. Fish & Wildlife Service, the University of Rhode Island and the University of Massachusetts Amherst began studying bird flight patterns off the East Coast. The studies, funded by the U.S. Bureau of Ocean Energy Management (BOEM), provide data on offshore bird movements to inform conservation efforts.

The Block Island Wind Farm tracking station is one of 35 along the East Coast, including two receiving stations on the southern coast of Block Island. The 35 tracking stations are operated in collaboration with the Motus Wildlife Tracking System, a coordinated network to track migratory animals marked with digital VHF transmitters throughout the Western Hemisphere.

For the past three years, Peter Paton, a professor in the Department of Natural Resources Science at the University of Rhode Island, along with Kim Gaffett and Scott Comings of The Nature Conservancy and UMass researchers, have been using the Block Island tracking stations to help collect data on bird movements in Rhode Island Sound and Long Island Sound. The stations were active until mid-October, and will be re-deployed this spring, as 40 more piping plovers, and roseate and common terns are expected to be tagged this year. The birds are tagged from colonies in Buzzards Bay, Great Gull Island in New York, and in coastal areas of Rhode Island and Massachusetts.

Data compiled during the past three years by Paton and his colleagues will provide baseline information for the Block Island Wind Farm behavioral study, which began last year and will run two more seasons.

Results from these various studies will help agency and industry partners balance renewable-energy development with conservation and will guide the use of this technology at additional offshore sites in the future, according to Fish & Wildlife Service biologist and UMass Amherst researcherPam Loring.

Telemetry technology tracks the movement of “high-priority” bird species such as common terns and American oystercatchers, federally threatened species such as piping plovers and rufa red knots, and federally endangered species such as roseate terns.

Paton said the focus of the work is to understand how migratory birds react to wind turbines, particularly under conditions when it’s difficult for observers to see birds, such as at night or during bad weather.

This is done by placing tiny transmitters on birds that emit a signal every 5 seconds for about 160 days. The towers’ antennas detect the signal, and by having multiple antennas detect a signal, researchers can triangulate the position of a tagged bird to track its flight path.

Paton said the data will be provided to federal agencies, written up in a report, submitted to an academic journal, and presented at meetings.

“This information hopefully will be useful in creating guidelines for site placement and operation of offshore wind turbines,” he said. “Determining the mortality rates for the onshore environment is a little easier. You can count the carcasses on the ground. They are sometimes hard to find, as predators can beat you to the carcasses. But in the offshore environment, they disappear into the ocean.”

Each of the Block Island Wind Farm’s five turbines is 600 feet high, so, as Paton noted, if the birds they are tracking fly higher than that, their risk of collision is lessened. However, collisions are only part of the problem offshore wind turbines can present to birds. They can also disrupt important foraging grounds for such species as gulls and sea ducks.