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Federal Researchers Probe Mystery of Starving Maine Seabirds
11/30/2011   Reported By: Jay Field

If you're a tern chick, there's nothing better than the sight of mama, arriving with a beak full of fish. To grow, and ultimately survive, these baby shorebirds need steady access to the Atlantic herring that swim the cold waters of the Gulf of Maine in schools. Even with a steady diet of herring, only about half of all tern chicks born annually on Maine islands survive. This past year, though, something went wrong. About two-thirds of all baby terns died, many from starvation. Jay Field takes a look at what might be killing them.

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For a few years now, student researchers with the U.S. Fish and Wildlife Service have been setting up shop on islands off the coast of Maine for 12 to 15 weeks at a time. They've been looking at how productive the birds are, and at what they're eating.

"And some years, they're able to find herring quite readily and other years it's kind of hard for them to come by," says Brian Benedict, the deputy refuge manager at the Maine Coastal Islands National Wildlife Refuge.

Benedict says this has been one of those "other years." He says researchers have watched as adult terns have swooped in with beakfulls of butterfish instead of herring.

"Butterfish, the shape of them is more circular, rather than long and thin. So it's very hard for the terns to get it down through their beaks," Benedict says. "The chick will attempt to eat it, or sometimes, just reject it."

There are three different species of terns in Maine: the Artic, the Common and the Roseate. In a good year, they lay two to three eggs per nest and successfully raise one chick.

But this year, some tern pairs aren't raising any little ones and others are raising just one. Sometimes, says Bendict, this dip in the popualtion is a one-year phenomenon. But he says it also can go on for several years at a time.

"There's a lot of research that's going on right now. Herring is critical not only for terns, but a whole wide array of things throughout the Gulf of Maine, including whales," he says. "It's very hard. The ocean is a big place. And, you know, we're seabird researchers and we rely upon the fisheries scientists to provide good information about what's going on with the herring fishery."

Fisheries scientists like Dr. Matthew Cieri. "I know nothing about bird biology," he says. "We work in very separate worlds."

Cieri, who works for the Maine Department of Marine Resources, does know a thing or two about herring. "The herring population, actually, is one big spawning mass that ranges from pretty much the Hague Line, the border with Canada, all the way through, passed, Cape Cod."

Fish are fish, says Cieri. They don't look at geography the same way as land-based animals. Their migration and feeding patterns, for example, are more heavily dependent on temperature and salinity. So, Cieri says, it's entirely possible that the herring population is stable, but isn't as available to the terns becuase it's staying out farther offshore.

"So it's generally a colder water species," he says. "So there is some debate over whether there's a relationship with temperature."

Some scientists believe global warming could be heating up the water close to shore and driving the herring out to sea. Others say overfishing could be to blame.

Cieri suggests the possibility of a water temperature change driven by an El Nino-like phenomenon in the Atlantic Ocean. He says it's important that researchers figure out what's going on, in large part, because of the crucial role that herring and silvery fish play in the foodchain: "We joke among scientists that if it's small and silvery, it's lunch."


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