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By Peter Rejcek
Researcher finds special bond — and discoveries
— among giant petrels
Donna Patterson-Fraser moves swiftly across the rocks
on Humble Island, deftly leaping from stone to stone to
avoid damaging the fragile moss that forms a threadbare
carpet across the island and between the giant petrel
nests along her route.
She and fellow field team member Kirstie Yeager also
must weave around the small colonies of Adélie
penguins — packed into irregular circles where the
ground is stained light pink with guano — and the
muddy wallows created by elephant seals. To call their
combined smell “pungent” falls far short of
the reality. It’s as if everything at a seafood market
has turned strongly rancid.
But Patterson-Fraser and Yeager quickly pass the animals,
hardly wrinkling their noses at the birds or the ill-tempered
seals, the latter throwing their weight around to steal
penguin territory.
One monstrously big seal barks and jiggles dangerously
close to a colony. Weighing up to three tons, a bull can
easily flatten a colony’s fragile chicks, even though
some now stand nearly as tall as their parents do. Patterson-Fraser
pauses long enough to curse the bully, as one feisty Adélie
brays and jabs its beak at the trespasser, actually forcing
the elephant seal to retreat.
“The Adélies have a tough enough time already.
Now they have to deal with that,” says Patterson-Fraser,
referring to the growing population of elephant seals
on Humble. A changing climate along the northern tip of
the Antarctic Peninsula has sent the local Adélie
population into a steep decline over the last several
decades as sea ice, a key habitat, has significantly retreated
in duration.
But that’s not the story Patterson-Fraser and Yeager
are interested in today. They’re on Humble Island
to weigh and measure the snowy white chicks of southern
giant petrels.
It’s a job that members of Bill Fraser’s field
teams have been doing for more than 15 years now. Fraser
is the principal investigator for the seabird component
of the Palmer Long Term Ecological Research (PAL LTER)
program , a mostly ship-based ecosystem study across a
700-kilometer swath on the western side of the Antarctic
Peninsula.
The “birders” spend most of their energy tracking
the bird populations close to Palmer Station on some 20
different islands, though some work is done farther south
off the U.S. Antarctic Program’s research vessel,
the ARSV Laurence M. Gould . The ship supports the LTER
cruise every January, while the birders island-hop for
their annual seabird census from October to March on inflatable
rubber Zodiac boats.
In the early 1990s, Fraser’s work had focused on
the penguins and a few other seabirds, like the intelligent
and long-lived brown and south polar skuas. Patterson-Fraser
wondered why he didn’t also work with the giant petrels.
“There’s got to be a story here,” she
recalls telling Fraser, whom she started working for during
the 1991-92 summer field season.
But the birds had a reputation as being difficult to
handle. They “gaked” — a vile, oily stream
of stomach contents — to defend against enemies.
They’ll gak on you, Fraser warned her, but gave her
the go-ahead to try.
The warning didn’t deter Patterson-Fraser, a short
but energetic woman with a pale complexion burnished bright
red by wind. She picked out a loop of nests that she watched
for an entire season — basically becoming acquainted
with the birds.
“You’ve got to take the time to watch and learn
the signals,” she says. “They’re easier
than people. I’m not a people person. I’m animal
person. … You don’t have to second-guess what
they’re thinking, because they’re straight up
with you. And you never worry about them talking smack
after you left; they’ll just talk smack right to
your face.”
After making protracted introductions that first season,
Patterson-Fraser then proposed the team start tracking
the growth of the chicks as a way to assess the parents’
ability to care and raise them to maturity. Fraser repeated
his warning: You’ll get gaked on.
Every day she would visit the nests, gaining the birds’
trust. Every day, Fraser asked if she had been slimed
by giant petrel gak. It never happened.
“He was almost disappointed by that,” she says.
Within two years, she had gained the trust of the giant
petrels, which allow her to handle the chicks so she can
weigh them and measure their culmen, or beak. A scavenger
and predator, giant petrels are roughly the size of a
bald eagle, with a hooked beak that can easily rip into
whale flesh. They roost on rocky high points across the
islands, making their nests out of small stones or discarded
limpet shells left behind by gulls
Giant petrels finding unique breeding success near
Palmer Station
This season there are 27 nests on Humble to visit. While
it’s been six years since Patterson-Fraser has been
in the field — she’s remained at home in Montana
to fledge her own “chick,” as she puts it —
she moves confidently among her old friends.
Some parents greet her with a bird bark, but as she leans
in and reaches underneath their warm underbelly to pull
out a plump chick, they merely nuzzle her arm with their
razor-sharp beak, instinctively trying to nudge her into
the nest as one of their own brood.
“We have this very kickback, very mellow, subpopulation
out here,” she says. On the other Palmer area islands
— such as Stepping Stones, a grass-covered islet
with a high density of giant petrels — the birds
are not habituated and so more skittish. The birders limit
their work mainly to taking a census of the nests and
banding the chicks, sometimes climbing short but steep,
shale cliffs to do so.
But the Humble giant petrels are mild enough to allow
the birders to put small transmitters on their backs to
track their movements during the breeding season. Some
birds make long-distance hauls of more than 1,000 kilometers
over a couple of weeks to hunt for food.
She and Yeager hope to outfit two Humble birds today
with the GPS transmitters. It’s something of a subjective
judgment call, trying to feel which bird will be least
ruffled by the device, which stays on its back for up
to a couple of weeks. It’s also an economic decision
— the GPS transmitters cost $4,000 a pop.
“Not every one of them wants jewelry either,”
Patterson-Fraser says of the boxy instruments, which sport
a long antenna that extends toward the bird’s tail.
The operations are fast and painless for the bird. Patterson-Fraser
makes her normal approach, half-singing random rhymes
and promising the bird squid popsicles if he will cooperate.
She carefully pulls out a sleepy chick, which another
team member holds, while she slips a wooden egg underneath
the bird to placate its brooding instinct. She works quickly
to fasten the transmitter with waterproof tape and a couple
of zip ties.
In the last 10 years, the team has made about 275 transmitter
deployments on giant petrels. “We’re the only
program that’s been able to do that,” Patterson-Fraser
says.
Except for work done by British ornithologist Steven
Hunter, in the 1970s and 1980s, this is the only major
giant petrel study under way, she adds.
“No one else … has the data we do on breeding
biology and foraging ecology, which because of its very
long-term nature, now provides us with the opportunity
to address specific hypotheses. This is the next phase
of this study,” says Bill Fraser via e-mail.
What are they learning?
First, the birds are doing better than Adélies
in this region. Their nests have tripled from more than
200 to 600 in the last 30 years, while Adélie breeding
pairs have dropped from 15,000 to 2,500.
“My theory is that their flexibility as predator-scavengers
is what allows them to do as well as they do around Palmer,”
Patterson-Fraser explains. Many of the nests contain recent
snacks to illustrate her point, from partially munched
penguin legs to bits of squid and fish. Adélies
subsist mainly on krill, which are also sea ice-dependent,
and fish when they can find them.
Fraser says his team believes that the success of the
giant petrels may be coming at the expense of the Adélies,
particularly fledgling penguins taking to the sea for
the first time in February.
“We are starting to suspect that their effects …
on the population may actually be quite substantial, and
probably now constitutes a serious additional population
stressor,” he says.
Still, the Palmer region may be the exception to the
rule for giant petrel success, Patterson-Fraser notes.
In other areas, the birds are declining. They’re
extremely susceptible to human disturbances, such as aerial
over-flights and physical destruction of habitat, and
changes in weather patterns, particularly to winds and
precipitation.
“We’re finding more fishhooks,” she adds.
Indeed, during the team’s couple of hours on Humble,
they find a rusty fishhook near a nest. Patterson-Fraser
logs the find in her notebook, which contains a byzantine
code to the layman that tracks chick weight and beak length,
along with notes about behavior and other finds.
“This was not something that I had envisioned doing
for my whole life, but that’s how it’s looking,”
she says, skipping across the rocks to the next nest.
“It’s a lot of work, but it’s worth it.”
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Antarctic
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