First, you hear them. It is almost the sound of Canada geese, not quite cattle. More than anything, it is the sound of New Year's Eve: long, cheap plastic trumpets, hundreds going at once. The landscape holds no clues to the sound's origins. This is desert, a wind-harried patch of Patagonia called Punta Tombo, 750 miles south of Buenos Aires. You would never guess the noise coming out of this bright, hot, arid South American wasteland is the noise of 500,000 penguins, the largest mainland breeding colony of Magellanic penguins on Earth.

Most people don't know that Magellanic penguins bray or that they live in temperate climes (as do four of 17 penguin species). Most people, including biologists, don't know much about these birds. The bulk of what is known has been discovered by one woman, penguin specialist Dee Boersma. Boersma holds a teaching post in the zoology department of the University of Washington in order to carry out her research at Punta Tombo, which she has done every year for the past 19 years. The Magellanic Penguin Project is one of the world's largest studies of avian life— with 4,000 birds banded at any given time— and one of the longest running. It's the Harvard Nurses Study of birds.

Nearly a fourth of the Magellanic penguins in Patagonia nest at Punta Tombo, but their numbers are dropping by an average of 2.5 percent a year.

Boersma's single-minded persistence is more than equaled by her subjects'. Each April, they leave the security of their Punta Tombo bushes and burrows and embark on the lengthiest flightless migration of any bird— a seven-month journey up the coast of South America and back in pursuit of food. Streams of them come in at Punta Tombo every afternoon, pulling up at the exact same spot every time, as though it were a subway exit with a sidewalk leading up to the beach and into the colony. The following dawn, tiny suits make their way back down that same invisible sidewalk and into the sea again.

Until Boersma began attaching transmitters to small groups of penguins in 1995, no one had any idea where or how far these birds traveled. Dawdling and Chaplinesque on land, they hardly seemed capable of undertaking such a long migration. Yet once in the water, Boersma found, Magellanic penguins turn into biological versions of attack submarines: swift, maneuverable, and aquadynamic, crammed with sophisticated navigational gear, powered by an innovative digestive tract. Left to themselves, they can cross the trackless oceans as if on steel rails. The hard part is getting the modern world— whether in the form of oil tankers or global warming— to stay out of the way.

"We're the census people!" Boersma shouts one morning, over a wind that has chipped whitecaps into the turquoise swells and parted her blond pageboy just above one ear. "We want to know where they live, who they breed with, how frequently they get divorced . . ." She has been up since 5:30 a.m., making daily rounds of the colony, which covers a 4-square-mile area, with nests and burrows spaced a few feet apart. She wears her customary field garb: layers of heavily pocketed khaki, accessorized with a fanny pack the size of a Victorian bustle and leather-sided sunglasses to keep out the wind and sun.

Dee Boersma has helped band more than 50,000 penguins during her 19 years in Patagonia. Chicks are fully dependent on their parents for 30 days, and they fledge at three months.

Using the birds' flipper bands to identify them, she jots down data on who's back from the annual migration, who's nesting with whom, who's got an egg, who's had a fight, who's been evicted, who's got a chick, and who's lost one.

"This is a great nest you've got," Boersma tells a male penguin lying in a hollow depression under a thorny, knee-high bush. Boersma's studies show that the better shaded the nest, the better the bird's chances of attracting a mate. This male is on his belly, flippers flat at his sides, in the manner of a hog-tied prisoner. (This is the only way penguins can relax on land. They have a hard time sitting and are said to have trouble getting up off their backs. The British Antarctic Survey recently dispatched a ship to South Georgia Island to investigate rumors that low-flying aircraft were causing king penguins to look up so suddenly that they were toppling over backward and, unable to right themselves, dying. The very notion causes Boersma to snort into her coffee.)

Boersma kneels, her face inches away from the penguin's. Years of tourist contact have served to erase the birds' fear of people. "How many babies do you have?" Boersma talks to penguins the way she talks to journalists, with kindness and great patience, although she doesn't really expect them to understand. She is looking for birds with two chicks in the nest— the colony's most successful breeders. (Penguins typically lay two eggs each season, but it's relatively rare for both to survive.) Using satellite tags, she plans to track the activities of successful breeders at sea and compare them with those that have lost both their chicks or eggs. She hopes to figure out what the successful parents are doing differently. She suspects ocean-foraging skills are the critical factor.

Some gray fluff behind the bird turns out to be a pair of chicks. Bingo. Boersma readies her satellite kit. She is using a glue formulated for penguin exteriors made by a kindly epoxy chemist in Seattle. Boersma excels at what she calls "co-opting people." "He told me, 'Well, we won't make any money on this, but it's really interesting.' A few weeks later, he met me in the bookstore with two paint cans full."

Boersma uses a homemade "penguin stick," a sort of shepherd's crook, to gently roust the bird from its burrow. Penguins from neighboring nests come out to watch. "They're curious," says Boersma. "They always want to see what the giants are going to do." With the unhesitating mastery of someone who has done this thousands of times before, Boersma gets a grip on the bird and tucks him gently under an arm. The white of the penguin's tuxedo breast appears pristine, but he smells decidedly like wildlife. "Yup," says Boersma, "they're well-dressed, but they need a shower." The transmitter is about the size of a Snickers bar and will be glued to the lower half of the bird's back, where it will create less drag in the water. How does Boersma know that putting it there will create less drag? Because she put two dead, stuffed Magellanic penguins in the Boeing wind tunnel in Seattle and studied how the device altered the airstream in various positions.

Magellanic penguins are singularly unafraid— a useful trait, given the hordes of tourists that come to Punta Tombo every year.

She is pleased with the new penguin epoxy, which hardens to a flexible neoprenelike layer. Yet she knows that the transmitter won't be there when the bird returns. Eventually, the rigors of penguin life will prove too much for even the strongest glue, and $2,000 worth of electronics will sink to the bottom of the Atlantic. Boersma shrugs. "What am I going to do? Put a note on there saying 'Please drop in nearest mailbox'?"

On Punta Tombo's stone beach, the penguins lie side by side with their backs to the sea. It is as though, having spent seven months living and sleeping on the open ocean, they prefer to gaze at land. A Magellanic penguin may travel as far as 2,000 nautical miles north in pursuit of food, reaching the coastal waters of Brazil before returning to Punta Tombo to breed and raise young. (This year's travelers set a record, as evidenced by a handful that wandered ashore on the beaches of Rio de Janeiro, prompting confused but well-meaning beachgoers to take them home and refrigerate them.)

Penguins are built for speed and efficiency in the water rather than in the air. Their ancient, petrellike ancestors had hollow skeletons like other birds, but their bones filled in and became heavier over time, enabling them to dive deeper and catch more fish. (The schools of anchovy and other fish that Magellanics eat frequent depths of 30 yards or more.) Like almost all flightless birds, the first penguins lived on islands with no native predators, so flight, in either sense of the word, wasn't a necessity. Over millennia, the penguins became more like sea creatures and less like birds. Their wings became flippers, which they use as sea turtles do, to propel themselves underwater. They evolved a hydrodynamic shape that reduces drag in the water, and a thick layer of fat. Their waterproof feathers can be raised (to cool off) or lowered to trap an insulating layer of air next to the skin. ("It's like having their own dry suit with lots of warm clothes on underneath," Boersma says.)

Members of the colony return to the same nest year after year, arriving in September, laying eggs in October, and hatching them in November.

What amazes Boersma most is not the length of the Magellanic migration but the predictability of it. "The route we saw them take in '97 was absolutely identical to the one in 2000," she says. "Somehow, the penguins know that there are roads out there. They travel these highways, and it doesn't look like they're much more than 50 or 60 kilometers wide. They might as well be on Route 66."

Route 66 has blacktop and road signs. The Atlantic looks the same in every direction. How does a Magellanic penguin navigate? "It may be as simple as this," Boersma says. "When food is scarce, move north, and move with the current until you hit it." Even birds that don't migrate have extraordinary directional skills. For starters, they have a built-in biological clock that they use along with the position of the sun (or, at night, the stars) to determine direction, at least on clear days.

The most sophisticated piece of avian orienteering equipment is an all-weather position-finding system built into birds' heads. In 1979, Charles Walcott, James Gould, and Joseph Kirschvink published a paper in Science announcing that they'd found microscopic particles of magnetite in the ethmoid region, the area between the nose opening and the front of the brain, in homing pigeons. Magnetite— or lodestone as it's more commonly known— is a strongly magnetic iron oxide. At one time sailors used it to magnetize compass needles. Avian magnetite is produced biogenically by the birds, although no one knows how. When a bird changes direction, Earth's magnetic pull on these particles shifts, causing them to realign themselves, as if they were tiny iron filings inside the animal's head. Bob Beason, head of biology at the University of Louisiana at Monroe, theorizes that the particles are attached to some sort of cellular membrane, and when they move they cause that membrane to deform. This change in the cell is sensed by receptors and reported to the bird's navigation command center, which then issues a change of course.

On Punta Tombo, chicks are weighed, measured, banded, and sometimes equipped with satellite transmitters. Some will live to the age of 30, so the research is necessarily long-term.

Beason once built a powerful magnetic coil in the campus planetarium and used it to create mock shifts in Earth's magnetic field. He then took some large, funnel-shaped cages, covered their bottoms with ink and their sides with newspaper, and filled them with birds. The birds would invariably try to escape from the top of the cage in the direction that they would usually migrate, leaving telltale marks on the newspaper. But whenever Beason shifted the magnetic field, the birds would change course accordingly. This magnetic positioning system is often a bird's primary reference, Beason says, although they complement it with cues from the sun or stars. Some species calibrate their celestial compasses based on the magnetic field; others calibrate the magnetic system based on information from their celestial compasses.

All these evolutionary innovations and more come into play long before Magellanics begin their epic migrations. According to a study published last year by French biologists Michel Gauthier-Clerc and Yvon Le Maho, for instance, king penguins are able to hold food in their stomachs for up to three weeks, turning it from a digestive device into a grocery sack. (Magellanics seem to have the same knack.) It's not known how penguins do this, but Boersma thinks that they may somehow change their stomach pH. As a result, after they range extraordinary distances in search of food, they can save it undigested and use their navigation systems to find their way back home to deliver it to their chicks.

Back in the 1980s, before the satellite and digestion studies had come out, Boersma tried to establish a marine-protected area around Punta Tombo. She knew that penguins rarely top 8 kilometers per hour (5 mph) in the water, and that they typically need eight hours to digest a stomachful of food. "So we figured, okay, if they're feeding their chicks they need to come in with about half a stomach of food. You use your higher math skills and you multiply 8 times four hours and round it off, and you get about 30 kilometers." Then came the satellite-tracking study. Boersma's calculations were off by a factor of 20, it showed, and a 30-kilometer preserve would hardly protect the penguins. "In many cases, we know these birds are going five, six hundred kilometers away from their nest site while their mate is sitting around on the eggs. No one had any idea they would go that far," she says. "And we'd never have known if we hadn't glued those tags to the backs of those birds."

Thanks to their sophisticated navigational skills, migrating Magellanics stick to the same route every year. Until recently, some 40,000 died annually along the way because of oily ballast water from tankers. But Boersma's research and public opinion have convinced oil companies to alter their tankers' routes— and even to help fund her satellite-tracking research.Graphic by Matt Zang

Boersma and her students' work has touched on just about every aspect of modern penguinhood, but their main focus is reproductive success. The Magellanic Penguin Project was established by the Wildlife Conservation Society in 1982, when a Japanese company planned to slaughter 40,000 Punta Tombo penguins a year and make them into oil and golf gloves. Protests by conservationists convinced the Argentine government to wait until more was known about the birds and their population stability. Instead, the office of tourism joined forces with the Wildlife Conservation Society to launch a long-term study of the birds.

At first glance, the Punta Tombo population hardly looks endangered: You cannot walk three feet without spotting one in its burrow or standing around outside it. So numerous and so fearless are the birds that the colony has spawned a lucrative tourist trade. (Boersma has studied this, too, and found that the proximity of the tourist paths to the penguins' nests doesn't affect their reproductive success.) "People visit here and they see all these birds, and they get the idea that it'll be like this forever and we don't need to really worry about it," Boersma says. Yet her research shows that the colony has shrunk by a third since 1987, and it continues to decline.

Even if you stuck around for a few years taking head counts, you might not see the decline: The penguins' breeding success varies tremendously from year to year. "This is why it's so important to do long-term studies of wildlife," Boersma says, picking thorns from her vest. "If we'd stopped after three years, we'd have said that population density is the biggest factor in the survival of young chicks"— too many birds competing for limited resources means a low survival rate for new chicks. "Now we know it's not. It has to do with these windows of opportunity. If chicks fledge when the fish are right off Punta Tombo, they're going to have enough opportunity to learn how to forage, and then you'll have high survival."

This means that the well-being of the Punta Tombo colony depends on where the fish are and when. And this, in turn, depends on climate and climate change. Over the last year, a La Niña event caused a shift in the Atlantic currents. The water off the Brazilian coast was unusually cold, causing an upwelling of nutrients that made fish populations boom. The fish, in turn, drew the penguins much farther north than usual, which took a toll on the birds. Now they're arriving home late and in poor condition, laying smaller eggs, and unable to find enough prey close to home. As a result, this year the colony has seen its lowest survival rate among new chicks in 17 years.

Penguins are the most aquatic of all birds, with Magellanics spending as much as two thirds of their lives in the water.

Global warming is thought to be behind the recent increase in both La Niña and El Niño events. The uncommonly heavy rains of El Niño are also hard on the Punta Tombo colony. Last year, 85 percent of the chicks expired in two days of heavy rains, some smothering under collapsed burrows and others dying of hypothermia.

Boersma bends to pick up a dead chick, small and soft as a rabbit's foot on a key chain. "Was this your baby?" she says to a penguin standing in the opening to his burrow. The bird leans forward, rolls his head to one side and then back, as though trying to look up someone's skirt. "He's brandishing his beak," whispers Boersma. "It's supposed to be threatening." I remark that it seems sad for the dead chick to be lying so close to its parents' nest. Boersma laughs. "They don't care." Penguins are not, by and large, a sentimental lot. Boersma once did a study in which she swapped different-sized eggs from nest to nest, to find out which was more important to survival, egg size or parents (parents, it turned out). The birds were unperturbed. She tells the story of a bird they called Huele Feo (Spanish for "smells ugly"), who used his deceased offspring as a sort of sofa bolster, lying down against it in his burrow. "We removed it and he moved to a nest with another dead chick."

Moving on to nest #7126, Boersma finds a female previously mated to #3901, who is presently residing down the street, in a burrow with chick #22,532. Penguin "divorce" is another of Boersma's discoveries. "Most people think of penguins, of long-lived birds in general, as being extremely faithful," she says. "And some of them are. We've had partners who've been together 16 years. But many get divorced." Boersma found that those that do are more likely to have failed to fledge young in the previous year. "Which is not all that surprising," she adds. "If you fail with somebody, you try with somebody else."

A penguin's waddle may seem comical to these tourists, but a recent study showed that it is an unusually efficient form of locomotion— at least for a bird with such stubby legs.

Back at the truck, Boersma bends down, as though to check the tires. A Magellanic penguin lies nestled against the rubber, taking advantage of the shade. He is round and fat, like a slab of dough waiting to be rolled, which he very nearly is. Boersma shoos him into the scrub. "Happens all the time. They think it's the best bush they've seen in a while."

It's 8 p.m. now. The sun has left a residue of smoky pastel daylight on the horizon. The colors lie on the water's surface, which has grown calmer with the close of day. Under our feet, mussel shells crackle like pond ice. You can hear the low, quiet clamor of the tide pulling at the pebbled shore, and off behind us the honking-braying of the birds. I ask Boersma when she'll be done with her work at Punta Tombo. She answers that she will keep on coming here as long as she can continue to get funding. Her goal is ambitious but simple: to know all there is to know about these birds. "Most research studies that get done are two or three years and then it's on to something else," she says. "There's a perception that after a few years, we know it all. But that's rarely the case. In my view, it's these long-term studies that give us broad insight into what's happening in the environment."

What is less simple is raising the money to fund a project like this. "People understand the value of something like genome studies: Health, longevity appeal to all of us. But when you say you want to do a chronicle of all life on Earth, that you want to understand what an incredible world we live in, unfortunately, it doesn't have the same power." She pauses. "I'm sorry. You put in a dime and you got a quarter's worth, didn't you?"

We stand and watch the waves and the antics of the band of juvenile males who spend their time hanging around the beach. Though Boersma has passed the day doing exactly what she did the day before and more or less the same sort of thing she has done for the past 19 years, though her cheeks are chapped raw from wind and her pants are streaked with guano, she looks as intoxicated with the place as does a new visitor. "I can't imagine a better study site," she says. "I mean, if you like penguins."

For more information, photographs, and a fact sheet on the Magellanic penguin, see users.capu.net/~kwelch/pp/species/magellanic.html.