Bird watchers know where sea ducks like the surf scoter breed — across Canada and Alaska — and where they spend their winters — along the U.S. coasts, in bodies of water like the Chesapeake and Delaware bays. Where they go in between is a bit of a mystery.
But with wind turbines possibly dotting the horizon off of Ocean City beaches by the end of the decade, potentially creating a new obstacle on the birds' migration routes, answers are needed.
Teams have spent three years in waters from Long Island to the Carolinas in search of surf scoters and two other types of sea birds, capturing them and releasing them with tracking devices. Scientists finished their tagging last month and have begun collecting data on their movement patterns, planning to continue following the birds as long as possible.
The study aims to more clearly map the routes the birds take between seasons, and to learn whether they cross a 125-square-mile zone established for possible wind farms. Early data suggests the birds stay closer to the coast than the wind farm zones, but more still needs to be learned about how the turbines could affect wildlife, scientists said.
"We had to find out: What are the pathways they use in migration?" said James Woehr, an avian biologist with the federal Bureau of Ocean Energy Management, which oversees offshore energy production. "The interstate skyway — is there any such thing?"
As many as 125 wind turbines are expected to be built about 12 to 27 miles off Maryland's Atlantic coast by 2020, according to U.S. Wind Maryland. The company is a subsidiary of Italian renewable energy firm Renexia, which won an auction in August for the rights to develop wind farms off Maryland's shores with an $8.7 million bid. The company estimates the project will require $2.5 billion in investment, according to its website.
Company officials said they plan to take the study and others into account.
"We want to do everything we can to not impact negatively the migration patterns of birds," said Paul Rich, director of project development for U.S. Wind. "I think we've seen from the history of offshore wind in Europe it has not been an issue. It certainly is something we should and will have to take into account."
But questions remain about how such projects would affect wildlife, including not just birds but also fish, whales, dolphins and seals. Land-based wind farms are frequently criticized for bird strikes, though there is some debate over how many birds are actually affected.
To explore how offshore farms could influence bird populations, scientists at the Bureau of Ocean Energy Management and the U.S. Fish and Wildlife Service chose to track three species of sea birds considered representative of larger bird populations: the scoters, red-throated loons and Northern gannets.
While much research has been done over the past decade to learn more about where those birds congregate during winter, there hadn't yet been a study that closely tracked their movements, Woehr said.
"There have been a number of surveys that have tried to look at concentrations at different times and places … and it's critical in understanding where to put these offshore wind turbines," said Caleb Spiegel, a wildlife biologist in the migratory birds division in the wildlife service's Northeast region. "But there's a piece of information missing — how are these birds moving on much finer scale?"
Biologists estimate that anywhere from a quarter-million to a half-million surf scoters winter along the U.S. Atlantic coast, while 240,000 Northern gannets and about 100,000 red-throated loons pass along the East Coast in winter. The birds spend their breeding seasons in Canada and fly south for winter.
It's not clear what hazards offshore wind turbines could pose to them. The towers could create new habitats for fish, which could draw birds into the path of their blades, for example, said Gwen Brewer, science program manager in wildlife and heritage service at the Maryland Department of Natural Resources, who is not involved with the study. The gannets scan waters to forage for fish at altitudes of 200 feet before diving down to feed, she said.
"If you've created a fish habitat next to a turbine then you've really created a potential danger zone there," Brewer said.
Catching and tagging the birds has been a complex feat for researchers, who started the $1.4 million study with trial and error as their only tactic, said Alicia Berlin, a wildlife research biologist at the U.S. Geological Survey's Patuxent Wildlife Research Center in Laurel. The research center took charge of efforts to catch and tag the scoters in the Chesapeake and Delaware bays and in coastal bays of North Carolina.
Teams of four or five people would venture out on overnight trips in a small motorboat with no lights but a spotlight from the bow, scanning the waves for groups of male scoters courting a lone female. Like a deer in headlights, the birds freeze when the spotlight hits them.
The researchers learned quickly that the best conditions for catching the birds were the least comfortable for them — 2- to 3-foot waves, rain or cloudy skies and 20 mph winds allowed them to sneak up undetected, said Berlin. They would approach the birds heading into the wind, coming alongside them so if they tried to fly away, they would hover in place, allowing the scientists to easily scoop them up with a net.
Then the team would either surgically implant an $1,800 satellite transmitter into the birds' abdomens — administering anesthesia and sewing up the wound within 20 minutes or so — or attach a backpack-style transmitter.
Both types of transmitters have drawbacks — the backpacks traditionally have been unwieldy, potentially making it difficult for birds to go about their normal foraging and flight, while the surgery required for the implanted transmitters could weaken them. About 20 percent of birds captured in the study died, researchers said.
But newer, solar-powered versions of the backpack transmitters are less cumbersome to the birds and also can last as long as three years. The researchers plan to follow the birds as long as they can.
"We're not going to throw away that data," Woehr said.
The scoters are all expected to head north to their breeding grounds by the end of May, giving the researchers at least one season of data for starters. Though some bird lovers and wildlife advocates are quick to criticize the wind turbines' potential impact, scientists said it's still too soon to come to any conclusions.
"There's just not enough science there for me to have an opinion," Berlin said. "The scientific community feels like we need to get more information to make a call as to what the influences are going to be."