Saturday, December 11, 2010

Penguins at risk

Research trip to the Antarctic: Penguins at risk - December 10, 2010

penguincensus.jpgPosted on behalf of Jane Qiu
Science journalist Jane Qiu is at the Palmer ecological research station on the Antarctic Peninsula, joining researchers investigating how climate change has affected the region in recent decades. Please check back for her dispatches from the bottom of the world.
If the Marr Ice Piermont glacier is the backyard of the Palmer ecological research station in western Antarctic Peninsula, the tiny speck of rock known as Torgersen Island, less than one kilometre from the outpost, is its front garden. Boasting the largest penguin colonies in the region, the island is a popular destination of after-dinner strolls for people at Palmer, and is visited regularly by tourist cruises.
A roughly circular island 400 metres in diameter, Torgersen is one of the four islands around Palmer where Jennifer Blum, an ornithologist of the Polar Oceans Research Group (PORG), a not-for-profit organization in Sheridan, Montana, and her colleagues perform regular seabird surveys. It’s Blum’s sixth season at Palmer, but the studies go back to 1975.
On an overcast day in late spring, I accompany the researchers on one of their survey trips. Adélie penguins – half-metre tall creatures with white “tuxedo shirt” in the front and white ring around their eyes, and one of the two penguin species that breed exclusively in the Antarctic – huddle in groups, or colonies, ranging from a couple of dozen to hundreds.
penguins11.jpgMost of them are nestling down, covering the eggs on top of their feet under a loose fold of skin called the brood patch. This specialized part of their body contains numerous blood vessels and allows the animals to incubate their eggs at 30 degree centigrade – even when the ambient temperature hovers around zero in the Antarctic spring.
Blum and her team members, Mark Travers and Kelsey Ducklow, walk around the island and count the number of nests and penguins in randomly selected colonies. Such censuses aim to track changes in the nestling process, especially damage to the eggs due to predators or accidents caused by penguins themselves.
Early on during the breeding season, the birders recorded the number of active nests when most adult penguins had bred. In a few weeks, they will count the number of chicks that have hatched and, when the juveniles are ready to fledge, the researchers will measure their bill size, flipper length and body weight. “These data will tell us penguins’ breeding success,” says Blum.
There are less than 2,000 breeding pairs of Adélies on Torgersen – compared to about 8,000 when surveys started in the 1970s. Blum points to a large patch of stones in front of us. “There used to be a large penguin colony here,” she says. Adélies make rocky nests out of small stones by carrying them in their beaks and dropping them in place, she explains. “They are all gone now.”
Torgersen is not the only island around Palmer that has seen a marked decline in Adélie population. Over thirty-five years, the total number of breeding pairs in the region has dropped by 80%, with the current population of less than 3,000 pairs, says Blum. “Even in the last six years since I’ve been there, changes have been quite dramatic.”
squab.jpgAfter the penguin survey, the birders walk to a few locations where brown skuas have nested, for another census. The southern species feeds on and times its breeding season to penguin eggs and chicks. The decline in penguin population is having a knock-on effect on brown skuas, says Blum. “They have really been struggling,” she says.
To researchers like Blum and Fraser, the marked decline in seabird population in the past few decades is a sign of deterioration of the marine food web in western Antarctic Peninsula. In the past 50 years, the average winter temperature in the region has increased by 6°C, over five times the global average; 87% of the glaciers are retreating and the ice season has shortened by nearly 90 days.
The reduction in sea ice has caused a cascade of changes in the marine ecosystem. The production of phytoplankton, microscopic plants growing under the ice which are the starting point of the food chain, has decreased by 12% in the past 30 years. Krill (shrimp-like creatures) and silverfish, which are key food sources for most predators in the Antarctic and rely on sea ice to survive, are also hard to find. “Adélie penguins are likely to go extinct in western Antarctic Peninsula in a hundred years or sooner,” says Fraser.


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