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Rabbits ravage seabird populations on Destruction Island
On islands around the globe, invasive European rabbits wreak such havoc on plants and seabirds that governments worldwide have spent a century trying to eradicate the furry beasts. Now the U.S. Fish and Wildlife Service is making plans to try its luck on Destruction Island, a 30-acre outcropping off the rugged Washington coast southwest of LaPush.
Seattle Times environment reporter
DESTRUCTION ISLAND —
Peter Hodum crouched high above the crashing surf and jammed his arm into a tunnel of dirt.
An infrared camera was strapped to his face, and his right hand held the cordlike lens, which he snaked through a long earthen bunker that had been dug by a bird.
The biologist and his colleague, scientist Scott Pearson, had come to this steep uninhabited pile of rocks to catalog the decline of the rhinoceros auklet, a gray seabird that nests deep in hollowed-out hillside burrows. But instead of spying one of the white-eyebrowed creatures, Hodum came eye to eye with the most likely cause of its decline.
"Oh, there's a rabbit in here!" Hodum whispered. "Wow, look at that. I see you!"
Even here, in one of the Northwest's most remote places — an out-of-the-way island so wild and ecologically sensitive it is now largely off-limits to people — humans have managed to upend the natural system.
And we did it the way we have on more than 800 islands around the world: We brought bunnies.
From the Channel Islands in California to our own San Juans to islands off Chile, North Africa and New Zealand, invasive European rabbits wreak such havoc on plants and seabirds that governments the world over have spent a century trying to eradicate the furry beasts. Now the U.S. Fish and Wildlife Service is making plans to try its luck here, on a 30-acre sea-swept outcropping off the Washington coast, 17 miles southwest of LaPush.
It can be a prickly problem. Cottontails, to some — especially in North America — remain a sort of charismatic cuddly fauna. For years, nearly 500 toothy, grass-guzzling, invasive rabbits transformed San Juan Island's American Camp prairie into what the National Park Service dubbed "a moonscape." But the agency two years ago backed off plans to shoot and trap the animals after a public outcry. The Park Service is conducting a more detailed environmental analysis.
Still, islands are home to some of the planet's most exotic creatures and scientists increasingly consider them important ecological safe harbors. Globally, the vast majority of species extinctions have taken place on islands. And the most common reason those animals disappear: introduced nonnative species, such as rabbits.
"Island ecosystems are unique, and the species that use them can be like the canary in the coal mine for global warming, ocean acidification, and all sorts of other ocean issues," said Kevin Ryan, project leader for the Washington Maritime National Wildlife Refuge Complex, which oversees Destruction. "It's important to maintain these areas for sentinel reasons."
The waters around Destruction are an important breeding ground for sea otters, auklets, troubled populations of tufted puffins, common murres and red-beaked oystercatchers. Those waters are also visited by an array of harbor seals, sea lions, porpoises and bald eagles.
But some animals' feeding patterns are changing in odd ways and that may be helping drive down populations of auklets and puffins.
Perhaps more importantly, the island's native vegetation is in transition, as hungry rabbits chomp away at once knee-high perennial grasses, allowing invasive annual grasses to take their places. The rabbits keep these new grasses so short they are no longer enough to hold steep hillsides together. The cliffs erode sooner than expected, prompting bird burrows to collapse into the sea.
Three miles off shore, just south of where the Hoh River meets the Pacific, the jagged crags and rocky shelves that form the base of Destruction Island meet steep mud cliffs and spongy, grassy banks that rise 80 feet to a tabletop of green.
It's these steep earthen slopes that drew Hodum, a bird biologist from the University of Puget Sound who regularly studies seabirds in South America, and Pearson, with the Washington Department of Fish and Wildlife.
The damp grass and moist earth are heaven for tunneling seabirds, which have scraped out thousands of long, winding dens to rear their young. The men arrived here on a sunny day to gauge how many burrows were occupied and how many bird pairs were successfully producing chicks.
The scientists, both former rock climbers, hoofed uphill as nimbly as mountain goats onto unstable grassy hummocks. They stepped gingerly around fragile bird eggs and over pellets that had been regurgitated by eagles.
With infrared cameras over their eyes — Hodum jokes that the get-up makes him look like Lt. Cmdr. Geordi La Forge from "Star Trek" — they threaded lenses into tunnels stretching eight or nine feet into mud. They jotted notes anytime a blinking auklet stared back.
"All right, OK," Hodum shouted as he stood exposed on the cliff, his back to the sea. "I've got an adult and eggs on both of these two."
Pearson, seated near a burrow about 10 feet away, said: "Peter's probably probed more burrows than anyone else in the world."
"That's how simple-minded I am," Hodum said, laughing.
As the two moved along the high cliffs quickly documenting bird reproduction, Pearson explained the problem. While auklets appear to be doing exceptionally well on Protection Island in the Strait of Juan de Fuca, researchers have seen a 60 percent decline in burrows on Destruction Island since 1975. And Destruction is one of the species' biggest nest sites globally.
Meanwhile, tufted puffins, another crazy-beaked squat seabird, are far rarer on Destruction. But they're also declining throughout much of the Northwest and are so skittish they're difficult to study on other offshore islands.
The two species are like the yin and yang of burrowing seabirds. Tufted puffins feed their young during the day and are easily driven from their nests. Auklets feed their young at night, but, as Hodum and Pearson demonstrated, they can prove pretty hard to spook.
Agitating an ecosystem
After a day of cataloging bird burrows, the two researchers crept through the willows in near darkness to watch their subjects finally arrive.
It was 11 p.m. when the first of the rhinoceros auklets showed up. It crashed through the willows like a winged mouse in free fall. Then it corrected its sloppy dive with a delicate landing in the dirt inches from Hodum's head. This bizarre fowl with the tiny horn near its bill stared at the biologist for a split second, then skittered beneath the bushes and into its dirt burrow.
Auklets spend their days at sea and return at night with beaks full of fish to deliver to their young, tucked in darkness in burrows. Their relative comfort around humans is one reason researchers study these birds as a stand-in for other island seabirds.
"We're also trying to use seabirds as indicators of marine conditions," Pearson said.
But of course they can't do that if the birds don't survive, and on Destruction their chief nemesis isn't at all hard to spot. Sometimes you just have to follow the eagles.
Early one afternoon, the researchers crested a slope not far from where the birds land at night. Giant brier patches of willows cover the flat top of this island, but the willows open occasionally onto grassy pads, each as well-groomed as a putting green.
On one patch, an abandoned lighthouse and outbuildings serve as reminders that this place remains the only offshore island of significance between this stretch of Washington coast and California's Farallon Islands. The lighthouse protected sailors for 117 years, until the Coast Guard turned the lights off in 2008.
After a few minutes of quiet stillness near these decaying buildings, a dozen or more eagles began to circle above. As the predators rode thermals, brown bunnies — some no bigger than squirrels, others as large as small dogs — quickly hopped into the shadows.
"See how cropped this grass is?" Hodum pointed out later. "We'd never have this without rabbits."
These rabbits, native to southern Europe, have found their way onto islands for centuries, as stowaways on boats, brought intentionally by game enthusiasts for hunting or for food, or by settlers who kept them as pets.
While no one knows for certain how they reached Destruction, scientists and land managers have gathered evidence in support of a theory: A lighthouse keeper used to live on the island, and local lore suggests his daughter kept rabbits as pets. Either the animals escaped, or someone set them free.
"It's not that uncommon," said Gregg Howald, with Island Conservation, a Santa Cruz, Calif.-based environmental group that travels the world getting rid of invasive species on islands. "Most lighthouses were manned by people and they brought their families and associated pets. A lot of those were left behind. I'm aware of at least one lighthouse island north of British Columbia that has rabbits that arrived just this way."
The fur balls have changed island ecology in many ways. Scavenging rabbits have mowed down thigh-high luxuriant perennial grasses. Nonnative annual grasses have risen in their place, but rabbits keep them so sheered they barely rise above boot heels.
Without grass, the muddy hillsides, always subject to slow erosion, crumble faster into the sea. That leaves less earth and more rock on hillsides, which can't be transformed into bird burrows.
Meanwhile, the rabbits have helped draw in ravenous bald eagles that hunt for the bunnies — and gnaw on rhinoceros auklets.
And the eagles' presence often is enough to keep tufted puffins from entering their burrows. That can drive the troubled seabirds away just as their young need food.
"Sometimes the puffins just stay away and decide not to breed at all," Pearson said.
And sometimes, though it's rare, rabbits even wander into auklet burrows and drive out the birds for good.
The researchers hope to do more to catalog the cascade of impacts from rabbits. In the meantime, they and Ryan, with Fish and Wildlife, are in the early stages of making plans to try and remove the rabbits. The planning and budgeting process could take months or even years.
But, they hope, by shooting, trapping or poisoning Destruction's rabbits, they could fairly easily restore a bit of balance to a rich Northwest island community.
Howald, with Island Conservation, said the ecological track record for water-locked communities that removed invasive rabbits is quite good, even for islands home to burrowing seabirds. The numbers of pink-footed shearwaters, a similar species on a South American island where Hodum also does research, rebounded in about three years after rabbits were removed there.
"We know what the mechanism causing the changes appears to be," Pearson said. "And we know we can do something about it."
Craig Welch: 206-464-2093 or firstname.lastname@example.org. On Twitter @craigawelch.