By GLEN MARTIN
San Francisco Chronicle
April 04, 2007
This is the third year that scientists have found unusually large numbers of marine birds - mainly common murres, but also rhinoceros auklets and tufted puffins - washed up on beaches in California, Oregon and Washington. In 2005, the first year of the phenomenon, large numbers of Cassin's auklets also died.
Hannah Nevins, the coordinator for Moss Landing Marine Laboratories beach survey program, said 253 dead murres were recovered on 11 Monterey Bay beaches during the first week of March. During the past nine years, an average of nine dead birds were collected on the same beaches during the same week, she said.
About 180,000 breeding murres live along the West Coast, so it is unlikely the recent spate of deaths is enough to drastically harm the overall population.
"But if this continues for multiple years, then we could have real problems," Nevins said.
Most of the casualties were young birds that had just gone through their first winter.
"They were all in poor condition, and generally had empty stomachs," she said. "Either they were not finding food, or they were unable to capture the food they did find."
Bill Sydeman, the director of marine ecology at PRBO Conservation Science, a Bay Area group that specializes in avian research, said the deaths are worrisome because it now appears they are not isolated events. In the two past years, the winter deaths were followed by less successful breeding at the Farallon Islands, one of the West Coast's most productive seabird rookeries, he said.
"I would not be surprised to see the same thing this year," Sydeman said.
Sydeman said the trend appears to be linked to changes in the California Current - a vast oceanic stream that delivers cold, nutrient-rich water from the Gulf of Alaska to the continental West Coast. Plankton thrives in this water, forming the basis of a food web that sustains everything from small fish to whales.
Fluctuations in the current in recent years appear to have resulted in regions of warmer water that support less plankton, Sydeman said. That can also reduce upwelling, a seasonal phenomenon that results in the replacement of warmer water along the Pacific Coast with cold, nutrient-laden offshore water.
Yet Howard Freeland, a research scientist with the Institute of Ocean Sciences in Sidney, British Columbia, said the California Current generally has remained strong during the past two years, though he said there have been some fluctuations.
But Julia Parrish, an associate professor in the school of aquatic and fisheries science at the University of Washington, said the North Pacific Ocean appears to be in major flux. During the past two years, she said, offshore upwelling did not begin off the continental Pacific Coast until summer, two months later than usual.
That was bad news for the birds because the warm water provided them little food during the height of the breeding season, Parrish said.
The once generally predictable North Pacific currents, she said, are "swinging like a pendulum." For example, in summer 2006, an unexpected "super upwelling" happened off the Oregon coast, sucking in vast quantities of abyssal water that was so low in oxygen that a temporary dead zone formed along the coast.
Sydeman said the anomalies could be linked to global climate change.
"What's clear is that during the past decade, there's much more variability out there than there was during the preceding 40 years," he said.
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