Elegant Scavengers

Giant Petrels are a Bellwether Species for the Threatened Antarctic Peninsula

Giant Petrels are large scavenger birds that feed on dead seals, whales, penguins, squid or just about any other creature that dies on Antarctica’s Southern Ocean, which is why 19th Century sailors called them “Bone Shakers.” They also named them “Stinkers” since, when challenged, they can spit a vile fishy stomach oil up to six feet.

David Helvarg

But Montana State University seabird researcher Donna Patterson has another take on Giant Petrels. “I think Giant Petrels rule the Earth; they’re fantastic,” she says, climbing out of a black rubber Zodiac and moving past huge burbling elephant seals and squawking colonies of Adelie penguins on Humble Island, Antarctica.

Humble is located near Palmer Station, one of three U.S. research centers operated by the National Science Foundation on the world’s last wild continent. Palmer is on the Antarctic Peninsula, a 700-mile long continental tail where marine and polar climates converge, creating a bracing, wildlife-rich habitat of ice-cold seawater, blue glaciers and granite isles.

Patterson, who has a bright but determined attitude and a sun-reddened face, has spent the last 10 years working “on the ice,” the last seven in the company of Giant Petrels. The first bird she encounters is sitting on a nest of stones. It’s the size of an albatross, about 12 pounds, with a long tube bill hooking to a sharp leather punch point. She crouches down by it, talking quietly as the gray-and-white feathered bird begins cawing and clacking, spreading its six-foot wing span as Donna reaches underneath and pulls out a downy white chick for measurements and weighing. It took Patterson over two years of approaching the nests every day before the birds would let her handle their chicks.

Both male and female Giant Petrels share in the incubation, brooding and feeding. They start courting and nesting in October, Antarctica’s Austral springtime. By early November they begin egg laying, followed by a 65-day period of incubation. Within 16 days of hatching both parents can fly off in search of food while the growing chick waits alone for them at the nest.

Patterson’s work, like that of Britain’s Stephen Hunter, her colleagues Bill Fraser, Matt Irinaga, and other Antarctic seabird researchers, is helping to expand the world’s knowledge of these rare creatures. “I believe these are valuable birds that can tell us a lot about the environment in which they live,” Patterson explains. They’re individually long lived. I’m working with a breeding female that was first banded in 1965. They’re also small in number, about 50,000 breeding pair in total. Until 1966, we thought they were a single species. Now we’ve divided them between northern and southern types, both of which can be found around Antarctica. Northern Giant Petrels are more concealed, solitary nesters found in the tussock grass of sub-Antarctic islands. Southerners are more colonial, favoring open windy areas.”

The northerners are also dependent on seal colonies, eating placentas and dead pups. Southerners are more pelagic, feeding off the seas as well as other birds. Donna points out some penguin bones near one of the bird’s nests. “Around the nests we’ve also found seal skin, squid beaks and krill,” she says. “They’re doing their job cleaning up the Southern Ocean.”

Patterson and Fraser meet up on nearby Kristie Cove; they stand on a rocky beach rimmed with brash ice, looking over their census papers. These track each bird’s island of origin, nest number and band number (for leg-banded birds).

One of the things these censuses (and the return of bands found on dead birds) has helped to establish is the recent decline of the species’ population. As many as 100,000 Antarctic seabirds, mainly Albatrosses, but also Giant Petrels, are now thought to be dying every year in encounters with long-line fishing fleets that have expanded their operations into the Southern Ocean. The birds dive for the baits as the long lines, often containing several thousand hooks, are unreeled from the high seas fishing boats. If the birds catch the bait at the surface they are often dragged under and drowned, or else entangled and injured.

“We’ve found hooks and lines around the nests as well as hooks engorged in the birds’ throats,” Patterson reports. As a result, slow-to-breed Southern Giant Petrel populations are now crashing, along with various species of Albatross.

Much of the long-line fishery threatening the birds involves the unregulated and often illegal taking of Patagonian toothfish, a deep water Antarctic species that biologists believe is also being pushed towards extinction by overfishing. Toothfish are misleadingly labeled, shipped and sold in the United States as Chilean Sea Bass.

Another concern in Patterson’s study is climate change, which has accelerated at the poles, with the Antarctic Peninsula having experienced a 10-degree increase in winter temperatures in just the last 50 years. “This warming trend could affect Giant Petrels in that we’re seeing more elephant seals moving south. An increase in elephant seal populations could prove disastrous for nesting Petrels because of the competition for space,” she explains. “Also, warming has increased precipitation in the form of snow, and if there’s too much snow that could reduce their nesting sites.”

Four Giant Petrels have now been equipped with tiny satellite tracking transmitters. Every day via e-mail, Patterson receives satellite-generated color photo/maps, tracking the routes of her foraging birds. Two recently traveled down to the continental ice edge, to destinations 680 and 720 miles away. She notes that after feeding there for several days, they rode a storm system back to Humble, arriving in just 10 hours.

In coming years, Patterson hopes to expand this kind of remote sensing in order to learn more about Giant Petrels, their habits and behaviors. At the same time, she fears that if unregulated fishing fleets continue to roam the Southern Ocean, these birds could disappear from Antarctica’s skies. “Petrels are good indicators of the health of this ecosystem,” she explains. “But if we let them go extinct because we consider them a ‘trash’ species, what does that tell us about our own species?”