Arctic Geese Skip Migration as Planet Warms

Discovery.com, Sept. 16, 2009 

In the Fall of 2007, tens of thousands of small arctic geese called Pacific brant (Branta bernicla nigricans) decided not to go south for the winter.

For these long-haul migratory birds, it was a dramatic choice -- they usually spend the cold months munching their favorite eel grass in the waters off Mexico's Baja peninsula. But changes in Earth's climate have so affected them that the barren windswept lagoons of western Alaska are looking more and more appealing.

The trend is likely to continue, according to a new study, affecting not only brant but a host of migratory birds around the globe.

David Ward of the U.S. Geological Survey in Anchorage has been studying brant behavior for nearly three decades.

When he began back in the 1970s, only around 4000 birds toughed out the winter in Izembek Lagoon, a 25-mile long stretch of protected water on the Alaska Peninsula. Two autumns ago, the number had climbed to 40,000 -- nearly 30 percent of the total population.

"The birds normally wait for a storm system to come down through the Aleutians," Ward said. "They catch the tail winds down south. But the track of storm systems is a little different now."

Changing winds have been accompanied by warmer weather, which means less ice covering Izembek's eel grass-rich waters. It's a buffet for the brant, which can feast through the winter without having to make the arduous journey several thousand miles south and back.

Come spring they are the first birds back to the breeding grounds, and often the most successful at raising their young.

In fact, conditions are so good that the geese run the risk of overpopulating, according to Robert Trost of the U.S. Fish and Wildlife Service in Portland, Ore. The Pacific brant population hasn't grown much in size over the years, but an increasing food supply could lead to an explosion of birds in the next few years.

"Throughout North America and parts of Asia, geese are most influenced by springtime conditions," he said.

As spring thaws creep earlier in the calendar, geese will be able to raise larger clutches of young.

The honeymoon isn't likely to last. Brant and many other species that live on coastlines could soon see their habitats flooded by sea level rise and swallowed by rampant erosion, two consequences of human-induced global warming.

 "Right now it's conjecture to say what the long-term impact will be, but the prognosis is not so good," Trost said.