Todd McLeish: The mystery of the shearwater dieoff

Shearwater.

Via ecoRI News (ecori.org)

Aboard the University of Rhode Island research ship Endeavor during the first days of August, seabirds were abundant in the waters between Block Island and Martha’s Vineyard. The birds weren’t the focus of the trip — it was about providing local teachers with an opportunity to get hands-on science experience through the Rhode Island Teacher-At-Sea Program — but the birds couldn’t be ignored. They were constantly in view.

Most were shearwaters, long-winged birds that skim the surface of the waves as they search for marine organisms on which to feed. Last year at this time, however, many were unexpectedly dying and washing up on beaches throughout southern New England and Long Island, N.Y.

The population appears to be healthy this year, but scientists haven’t yet figured out the cause of last year’s die-off.

“We’re still trying to piece it together,” said seabird researcher David Wiley, research coordinator at the Stellwagen Bank National Marine Sanctuary, off  Massachusetts. “We’re studying their livers to look at their toxicology to see if something killed them. And a team at Woods Hole is looking at birds caught as bycatch in gillnets. But we haven’t come up with anything definitive yet.”

Scientists speculate that the birds, which breed on islands in the South Atlantic and migrate to the East Coast in summer, arrived in local waters last year in such poor physical condition that they couldn’t survive. Whether that is because of a lack of food, an accumulation of toxins, or something else entirely is unknown.

“It could be something here [in the North Atlantic] as well,” Wiley said. “It could be a toxic algal bloom that’s caused the problem here. That’s another thing to look into. But right now, it’s all speculative.”

Although few birds have been found dead in the region this year, Wiley and a team of scientists hope to find some answers in a continuing study of great shearwaters, the most common of the shearwaters in the region, that began in 2013. Each year they capture 10 shearwaters and place satellite tracking tags on them to monitor their movements. The researchers hope to learn how and where the birds spend their time in the region.

To capture the birds, they toss bait into the water from a small boat, and then use a hand-held net to catch any birds that get close enough to reach. They weigh and measure the shearwaters, place a band around a leg, take blood and feather samples, and release them back into the wild.

So far their research has confirmed that the most important feeding area for the birds is in the Great South Channel, a deep-water site east of Chatham, Mass. The area is also an important commercial fishing destination, where hundreds of the birds are caught and drown in gillnets annually, mostly in August and September.

“Everybody is eating sand lance — the birds, the whales, the fish — so that’s where the fishermen go, too,” Wiley said. “Sand lance is the key to the southern Gulf of Maine.”

A tiny eel-like fish, sand lance are a favorite food of humpback whales, sharks, cod and other ocean predators. They spend their nights buried in the sand on the seafloor. Their cyclical population abundance drives changes in populations of the species that prey on them. And when sand lance numbers are high, conflicts arise between the whales, birds, fish, and fishermen.

The scientists are trying to figure out how to reduce the fishing bycatch of shearwaters, but they have had little success to date. The fishermen bait their nets to attract dogfish, and the baiting attracts the birds. If they don’t bait their nets, the nets must remain in the water longer as the fishermen wait for the fish to arrive, which increases the likelihood the nets will capture or entangle whales, porpoises, and other marine mammals.

Four years of data from 40 great shearwaters has confirmed that the birds move around a great deal, making it difficult to employ management strategies to protect them.

“Some static management measures like marine protected areas may not be as effective as they used to because the ocean is changing,” Wiley said. “We may be able to use our satellite tagged birds to look at where the hot spots are occurring in almost-real time. Then management can be as dynamic as the oceans themselves. We’re trying to get ahead of the curve to see if there are other ways of managing the ocean.”

University of Rhode Island doctoral student Anna Robuck is examining the birds from a different perspective. She is conducting toxicology tests to determine whether they are contaminated with any of a long list of chemical compounds, from long-banned pollutants such as DDT and PCBs to such industrial compounds as flame retardants and perfluorinated compounds, which are used as water repellents and in non-stick cookware and many other consumer products.

While she expected to find some of the contaminants in the birds’ tissues, including DDT, which is ubiquitous in the ocean, she was surprised to find some of the more than 4,000 perfluorinated compounds in the seabirds at similar concentrations to those found in gulls that live in Narragansett Bay.

“That was totally unexpected,” Robuck said. “The shearwaters live in the remote South Atlantic, so we weren’t sure we were going to be able to detect measurable concentrations, because we were uncertain that the compounds would be found in the oceanic environment. They’re found in surface water in Narragansett Bay at much higher concentrations than offshore, so we’re not sure why they’re in the seabirds.”

Birds in the bay are contaminated with a different set of perfluorinated compounds than those in offshore waters, which suggests to Robuck that the compounds are finding their way to the offshore environment via the atmosphere.

She isn’t convinced, however, that the contaminants have anything to do with the mass mortality of shearwaters last year.

“The contaminants aren’t lethal in the way we saw happening to the birds last year,” she said. “No way was it related to their contaminant burden. There are so many variables at play. I thought we’d test for something and figure it out pretty quick, but it’s turned into something much more complex.

“It’s probably an interplay of a lot of things — oceanographic conditions, food, stress from climate change. It’s a lot of stressors adding up. It’s really sad to see.”

Rhode Island resident and author Todd McLeish runs a wildlife blog.

Todd McLeish: More seabirds in region turning up dead, perhaps from starvation

Great shearwater.

Walking on the beach at the north end of Block Island last month, Matt Schenck stumbled upon two dead and decomposing seabirds, which the avid birdwatcher identified as great shearwaters. While gulls of various species are commonly found dead on local beaches, shearwaters are an extreme rarity.

Except this year.

Hundreds of great shearwaters have turned up dead on beaches on Long Island and southern New England this summer, and no one seems to know why. In addition to the birds on Block Island, birders and biologists have reported dead shearwaters on Rhode Island beaches in Tiverton and Charlestown.

Shearwaters spend most of their lives far out to sea, where they soar just above the waves as they forage on small fish and other marine creatures near the surface of the water. Four species of shearwater — great, sooty, Cory’s and Manx — are typically seen in Rhode Island waters, though they seldom travel within sight of land. Most breed on remote islands in the South Atlantic.

According to Josh Beuth, a biologist for the Rhode Island Department of Environmental Management, shearwaters have been observed in large numbers from the shore this year, including from Jamestown, Newport and Point Judith. They have also been seen regularly from the Block Island ferry.

“There has been an abundance of sand eels in our local waters, which are a forage fish for shearwaters,” Beuth said. “As a result of them being closer to shore than usual, it would be more likely that they’d wash up on shore if they died.”

While prey may be abundant, some biologists, including Linda Welch, a U.S. Fish & Wildlife Service biologist who studies great shearwaters off Cape Cod, have noted that many of the dead birds are juveniles that have been thin or emaciated, suggesting that the birds have starved.

The dead birds began to show up on beaches in late June, which is about when they should have arrived along the East Coast after their long migration from their breeding grounds in the South Atlantic. By then, they were likely stressed and tired and hungry, which may have made them susceptible to any number of potential sources of mortality.

Wildlife pathologist Joe Okoniewski examined some of the dead shearwaters found on Long Island beaches, and he told The New York Times that the birds were not only thin but anemic. “The big mystery is: Why are they thin? On the surface, it looks like you know what happened — they starved,” he said. “But when you ask why, it becomes much more of a mystery.”

It is especially mysterious if prey is seemingly abundant, as it has been this summer in Rhode Island waters.

Robert Kenney, an oceanographer at the University of Rhode Island’s Graduate School of Oceanography, speculates that toxic algae from red tides may be playing a role in the bird deaths. He said a number of northern gannets, another species of seabird, have been found dead on Cape Cod beaches this summer. The only difference, he said, is that they are “in good condition, except for being dead.”

He noted that toxic algae may have also contributed to the deaths of some of the numerous whales that have been found dead along the East Coast and in the Gulf of Saint Lawrence this year.

Among those trying to find an answer is Julie Ellis, director of the Seabird Ecological Assessment Network at the Tufts University Veterinary Medical Center, which uses volunteers throughout the Northeast to regularly walk beaches to collect dead birds for study. She is reaching out to a number of animal diagnosticians throughout the region in hopes that together they can come up with a consensus of what is causing the shearwater deaths. She hopes they will have an answer next month.

Rhode Island resident and author Todd McLeish runs a wildlife blog.