Laura Nielsen for Frontier Scientists
The Bering Sea region hosts over 90% of seabirds breeding in the continental United States. Most of those birds are hardy migrators, breeding on Alaska’s coast in the warm season and then departing south, chased away by the cold weather. One group which remains is Guillemots, a type of seabird species which belongs to the auks — the family includes murres, murrelets, auklets and puffins.
Guillemots are special. They don’t migrate to far southern latitudes but fly only as far south as they must to find cracks in the ice revealing open water for fishing, usually no further south than the Bering Sea. As average temperatures in the Arctic warm, they’ve been able to overwinter in the winter pack ice that populates the Chukchi and Beaufort seas. From June to September they take advantage of the snowmelt to breed.
Because Guillemots remain in the Arctic they are an ideal indicator species. Scientists know that any behavioral or population changes they experience are due to changes in the Arctic environment, and not changes applied by non-local conditions. The Arctic marine ecosystem is undergoing shifts due to climate change, and those shifts affect the seabird populations.
Average temperatures in Alaska have risen at least 4 degrees Fahrenheit since the 1950s. At first it seemed that warming average temperatures were helping Guillemots. The birds require a minimum of 80 snow-free summer days to secure a nesting site, copulate, lay eggs, incubate and hatch chicks, then feed their young until the chicks can fledge. Before the 1960s, a summer with 80 snow-free days was hard to find in northern Alaska. As the north warmed, though, snow-free days arrived earlier and earlier every June, and the birds’ natural biological response was to push further north and to begin nesting earlier, taking advantage of the warm weather. The Guillemots population thrived.
Climate change is complex, though, and while earlier summers proved a boon, retreating sea ice has proven detrimental.
Black Guillemots like to hunt near arctic sea ice. The ice provides a sanctuary for plankton which are fed on by small fish like the Arctic Cod, the Guillemots’ favored food source. Zooplankton and Arctic Cod are links in the food chain which feeds fish, birds, seals, polar bears, and even whales. Sea ice: hosts prey, grants protection from predators, and provides a nursery for the fish, keeping Arctic Cod nearby. When the ice melts and retreats north, far from nesting grounds on shore, the Guillemots, whose foraging range is typically less than 15 km, cannot catch Arctic Cod to sustain themselves and their hatchlings.
“The edge of the Arctic pack ice melted away northwards, leaving a bigger expanse of sea between the land and the ice. The birds find their favourite prey at the ice edge, so this took it out of their reach. I began to see the young starving and dying in their nests. … I have known some of these birds for more than 20 years and have seen them raise young every year. I used to end the season with maybe 200 chicks fledged. In 2009, one chick survived.” –George Divoky*
George Divoky is a Research Associate at the Institute of Arctic Biology, University of Alaska Fairbanks. He studies Black Guillemots on Cooper Island, a remote barrier island 25 miles from Barrow (the northernmost town in the United States), and has done so every summer since 1975. You can read more about his work at Cooper Island at Friends of Cooper Island, and even sponsor a nest.
Seabirds like the Guillemots which feed on marine organisms are so strongly affected by climate factors like heightened temperatures and altered sea ice extent that they serve as a sort of weathervane. Understanding the effects of climate change on seabirds helps us better predict future trends facing the Arctic ecosystem, which is fragile and already facing drastic changes.
Human consumption of fossil fuels has added carbon dioxide and other heat-trapping greenhouse gasses to the atmosphere. Even a tiny shift can cause higher-than-average temperatures in the Arctic. High temperatures lead to ice melting. Melting glaciers add fresh water to the oceans, changing their salinity. Melting pack ice denies animals specifically adapted to the floes their habitat, while also reducing the amount of reflective surface area in the Arctic. Instead of reflecting back into space, sunlight soaks into the exposed dark-colored land and sea, which in turn warms the region still more. Permafrost melts, releasing yet more carbon dioxide into the atmosphere. These effects form a positive feedback loop.
Of course the global climate is complex. The Guillemots should know; while earlier snow melt allows them to begin nesting sooner in the season, it also threatens their growing chicks. Melting snow and ice engorges the air with moisture, leading to heavy September snowfalls. If the snows come too early, those heavy snows can trap the Guillemot chicks in the nooks and crannies which their parents chose as nesting sites to help conceal the chicks from predators. The birds face other threats too. Polar bears, bereft of the thick ice where they normally hunt seals, sometimes swim to land where the Guillemots are nesting and go after the chicks. Oil spills like the 1989 Exxon Valdez spill are catastrophic; dead arctic seabirds were collected after the Exxon Valdez spill, and the toll topped 36,000 birds.
Guillemots help climate scientists understand Arctic trends, a blueprint that can and will be applied to changes the globe over. Among what we know now is that the Arctic sea ice has receded at a rate of 3 percent per decade since the 1970s. Climate models predict that the Arctic Ocean will have completely ice-free summers by the end of the century. The realities we face will be profound, for us, and even more so for the birds.
* Arctic loner: My life as a climate-change drama http://www.newscientist.com/article/mg20927975.500-arctic-loner-my-life-as-a-climatechange-drama.html by Alun Anderson in New Scientist issue 2797, February 02 2011
Friends of Cooper Island : Monitoring Climate Change With Arctic Seabirds http://www.cooperisland.org/blackguillemots/blackguillemots.htm Accessed Nov 20, 2012
Canary in a Coal Mine, from PBS’ Scientific American Frontiers broadcast: Hot Times in Alaska http://www.pbs.org/saf/1404/segments/1404-1.htm June 15, 2004
Arctic Newcomer, an Alaska Sea Grant Arctic Science Journey radio script http://seagrant.uaf.edu/news/96ASJ/11.10.96_ArcticNewcomer.html Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks, 1996
Implications of Climate Change for Alaska’s Seabirds http://www.besis.uaf.edu/besis-oct98-report/Seabirds.pdf Bering Sea Impact Study, Oct 1998 report