Winged in­va­sion

The Star Malaysia - Star2 - - ECOWATCH -

IT HAD been a dozen years since the United States Govern­ment moved thou­sands of black­capped squawk­ing seabirds to East Sand Is­land, Washington, to re­duce their diet of en­dan­gered fish. Things have not ex­actly gone as planned.

The hope in re­lo­cat­ing the world’s largest colony of Caspian terns to this sandy mound near the river’s mouth was that they would eat more sar­dines and her­ring – and fewer young salmon and steel­head. And they have.

But the move came at a price. This year, the birds’ sum­mer re­treat was trans­formed into a place of vi­o­lence. A strange chain re­ac­tion in­volv­ing dive-bomb­ing ea­gles and ma­raud­ing gulls kept this colony from pro­duc­ing a sin­gle chick.

Yet even with this bizarre turn, the ac­tual num­ber of threat­ened fish slurped by birds is higher now than it’s ever been. That’s be­cause this same des­o­late scratch of ground in re­cent years has also be­come home to the West Coast’s largest gath­er­ing of dou­ble-crested cor­morants. Now, this small city of gan­gly, avian beasts swal­lows far more salmon than terns ever did.

“It’s alarm­ing. They’re eat­ing our lunch, ba­si­cally,” said Gary Fredricks, a National Marine Fish­eries Ser­vice bi­ol­o­gist. “As we try to save more fish, they’re eat­ing more, and we’re not get­ting ahead.”

Crit­ics main­tain, as they once did about terns, that fish-eat­ing birds are a dis­trac­tion from what re­ally ails Columbia fish stocks – trou­bled fish habi­tat and hatch­eries, hy­dropower dams and fish­ing.

But there may be no bet­ter place than East Sand Is­land to see how un­in­tended con­se­quences can up­end hu­man ef­forts to re-en­gi­neer the an­i­mal king­dom. Na­ture, here – es­pe­cially lately – is at its most un­pre­dictable.

“Right now I have to say: we re­ally don’t know what next year is go­ing to bring,” said Daniel Roby, an Ore­gon State Univer­sity pro­fes­sor who has stud­ied these birds for years.

Grow­ing numbers

On a sunny Au­gust af­ter­noon, seabird bi­ol­o­gist Adam Peck­Richard­son hoofed across a sandy beach soon to be swal­lowed by the tide. He snugged his hat to pro­tect his head from a hail of fae­ces.

“It’s go­ing to get pretty loud,” he said, then made a stooped dash to­wards a tun­nel formed by plas­tic fenc­ing that served as a bar­rier of sorts for a sea of birds. The sky erupted in screech­ing.

Peck-Richard­son ducked into the tun­nel and peered through a hole to take in East Sands’ cor­morant colony. The brown turkey-sized birds were ev­ery­where. They stood like sen­tinels on dead tree limbs, lined up along drift­wood and wad­dled to and fro like pre­his­toric pen­guins.

It’s hard to imag­ine this colony of 27,000 cor­morants only num­bered a few hun­dred just 20 years ago. Then again, many bird species that now call East Sand home weren’t here back then. In fact, East Sand Is­land’s ex­is­tence as a seabird par­adise ac­tu­ally be­gan with an­other bird on an­other is­land.

In the early 1980s, Army Corps of En­gi­neers con­trac­tors dredged the river for big­ger ships and dumped the spoils in a pile 22km up­river. That pile, Rice Is­land, of­fered soft sand, a lack of preda­tors and an end­less con­veyor belt of pass­ing fish. It at­tracted squadrons of Caspian terns from around the West that had been driven away from their prior haunts.

By the mid-1990s some 20,000 had ar­rived. Pan­icked re­searchers fig­ured out they ate up to 16 mil­lion salmon smolts a year. So the Corps of En­gi­neers in 1999 got a team of Marines to cover their pre­ferred sandy nest­ing habi­tat on Rice Is­land with wheat and build them a new sandy home down­stream on for­got­ten East Sand Is­land. They hoped terns would re­lo­cate and that East Sand’s prox­im­ity to the ocean meant the birds would eat more marine fish like an­chovies. It worked. Tern con­sump­tion of salmon dropped by about two-thirds.

But with re­searchers fo­cused on puffy-white, red-beaked terns, few no­ticed other fish-eaters had found East Sand, too.

No one knows why cor­morants started show­ing up in 1989. Re­searchers pre­sume it was in part the loss of bird habi­tat else­where around the West. Ef­forts to pro­tect terns and keep peo­ple off the is­land also may have bol­stered East Sand’s ap­peal.

By a half-dozen years ago, it was clear that cor­morants – who eat four times more fish than terns – were on their way to wolf­ing too many salmon, too. Only in 2010, how­ever, did sci­en­tists re­alise just how large that salmon ap­petite had grown: the cor­morants that year sucked down 19 mil­lion smolts.

Even with the re­duc­tion in salmon con­sump­tion by terns, the two colonies com­bined now were eat­ing 20% of the salmon smolts head­ing to the sea.

“When we came out with that es­ti­mate, the fed­eral agen­cies said, ‘This is the last straw. We have to do some­thing’,” said Roby.

Preyed upon

But by then, the terns faced a life­and-death duel. In­side a blind on the other side of East Sand Is­land, Peck-Richard­son and two young re­searchers gazed out over a mostly empty sandy patch. A few hun­dred Caspian terns re­mained, but weeks ear­lier they’d been packed here wing to wing.

“They’ve had a pretty rough sum­mer,” Peck-Richard­son said.

Roughly 9,000 pairs of terns ar­rived in spring pre­par­ing to nest and pro­duce chicks. By early June, their sum­mer of love was a dis­as­ter.

Nearly ev­ery day, a bald ea­gle swooped in, plucked an un­lucky tern and flapped away to en­joy its meal. The skit­tish terns would flush and flut­ter about in chaos, leav­ing their new eggs ex­posed to glut­tonous gulls. Then a tern-swip­ing great horned owl showed up, fol­lowed by a pair Pere­grine fal­cons.

“The gulls just started gob­bling their eggs,” Roby said. “It was may­hem. It would hap­pen over and over and over un­til there wasn’t a sin­gle nest on the colony that had any­thing in it.”

The terns had nested suc­cess­fully for a decade, but the pre­vi­ous year fewer than one in 10 pairs had re­pro­duced. Re­searchers blamed El Nino. This year no chicks sur­vived.

Sci­en­tists are not cer­tain what brought in the ban­dit birds, but sus­pect a late, wet, cold spring re­duced for­age fish in the es­tu­ary. With the mas­sive out­pour­ing of fresh­wa­ter driv­ing marine fish to sea, ea­gles and other birds of prey fo­cused in­stead on terns.

Terns are so long-lived they can sur­vive two years of no re­pro­duc­tion, but re­searchers now won­der how many will come back.

“It’s pos­si­ble that a poor year of pro­duc­tiv­ity may cause a larger num­ber of birds to at­tempt to breed else­where,” said Ore­gon State Univer­sity bird re­searcher Peter Loschl.

Roby agreed. “Caspian terns have evolved to move from colony to colony,” he said. “They’re al­ways on the look­out for new nest­ing op­por­tu­ni­ties.”

In some ways, that might help bird man­agers. They’d hoped to even­tu­ally shrink East Sand’s tern colony, and have cre­ated new po­ten­tial nest­ing sites from San Fran­cisco to Ore­gon. But the goal was never to drive off the birds en­tirely.

“Is this a por­tent of things to come?” Roby asked. “We’re not so sure.”

It’s also not clear if more preda­tors will come to like the easy pick­ings on East Sand Is­land.

“I heard there were sev­eral ju­ve­nile ea­gles sit­ting around each day watch­ing the show,” Fredricks said. “Per­haps they were learn­ing.”

Ei­ther way, it still leaves the is­land’s other bird prob­lem.

Ea­gles and fal­cons have rocked the cor­morants, too, but since the big­ger birds don’t flush in ways that ex­pose their young to gulls, the Corps of En­gi­neers is hunt­ing for new ways to re­duce the cor­morants’ chomp­ing of fish. Fed­eral man­agers have dis­cussed op­tions rang­ing from driv­ing birds off East Sand to killing some. It could be a year be­fore for­mal pro­pos­als are de­vel­oped.

Al­ready, bi­ol­o­gists have shown they could shrink the space in­hab­ited on East Sand by cor­morants, sim­ply by push­ing a fence line for­ward and ex­pos­ing the birds to hu­mans. “They re­ally don’t like peo­ple,” Peck-Richard­son said.

Roby, for one, hopes so­lu­tions al­low for at least some of both bird species to re­main on East Sand.

“As hu­man de­vel­op­ment pro­gresses along the Pa­cific Coast, there’s go­ing to be more and more of these sit­u­a­tions,” he said. “If we don’t make an ef­fort to pro­vide that habi­tat where we can, we lose the na­tive wildlife species.”

Still it’s un­clear, given the pat­tern on East Sand, whether mov­ing birds will fix the prob­lem – or if yet an­other un­ex­pected vis­i­tor will change the equa­tion. – The Seat­tle Times/MCT In­for­ma­tion Ser­vices

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