from rocky – 04/11/2007
Recent deaths of seabirds leave scientists puzzling
Birds uncommon in Oregon have been washing up dead on the coast in high
What’s killing the seabirds?
Tuesday, April 10, 2007
Seabirds rarely seen on the Oregon coast have been washing up dead in
unusually high numbers over the past month, possibly because warm ocean
waters in recent years have pushed out their normal food sources.
The birds are starving, with empty stomachs and breast muscles
shrinking as their ailing bodies burn muscle tissue to survive, say
people who have found and examined the birds.
"They also feel lighter than they should," said Mike Patterson, an
independent researcher in Astoria who keeps track of the trends.
What stands out about the die-off that emerged in early March and
picked up again a few weeks later is the type of birds involved. They
include horned puffins, parakeet auklets, mottled petrels and
thick-billed murres, all species that usually stay far offshore of
Oregon and rarely appear here, experts say.
This is the third year that unusual numbers and types of birds have
turned up dead, a pattern that some researchers suspect could be linked
to shifting ocean conditions driven by global warming.
Others say the trend is more complicated, with climate change only one
of many factors at play. Many of the birds live far from human view,
making their lives an avian mystery in which it’s not clear whether
they are dying of unusual causes, or in unusual places, or if ocean
currents are moving them in unusual ways.
Some biologists suspect the birds may have moved toward shore searching
for food because the herring they usually feed on this time of year
have been especially scarce.
That could be tied to warm ocean conditions over recent years. A flush
of cold, nutrient-rich water that surges up from the deep along the
coast in a phenomenon known as upwelling has come later than usual in
the past few years, said Bob Emmett, a research fisheries biologist
with the National Marine Fisheries Service in Newport.
He surveys herring numbers near the mouth of the Columbia River. Young
herring flourish in that colder water, but probably had a hard time
surviving in the warmer conditions that dominated instead. That would
have left fewer herring for birds to eat this year.
Herring "can rebound very quickly if the conditions are right, but they
can crash just as quickly," Emmett said. "They are kind of a harbinger
of what’s going on out in the ocean."
When herring do well, seabirds and salmon often do well, too. But when
they do not, the other species do not, either.
"If you don’t have herring around, it’s probably going to be hard on
salmon, too," Emmett said.
The good news is that upwelling started on time this year, enriching
coastal waters, said Bill Peterson of the federal Fisheries Service in
Newport. That promises a strong rebound in coastal species if the
upwelling continues, he said.
The upwelling can also backfire on marine life if it grows too strong,
though. In some recent years, it has been so powerful, that it carried
nutrients that fueled massive algae blooms. When the algae dies and
decays, it sucks oxygen from the water, leaving a so-called "dead
Very strong upwelling currents may also push herring far offshore,
making it more difficult for them to spawn and feed, Emmett said.
"If they can’t get to shore, their life history is broken," he said.
More than single cause?
But other researchers say the marine system is too complicated to blame
the bird deaths on a single cause yet.
It seems clear that either more birds are dying, or they are dying in
different places, or some combination of the two, said Julia Parrish, a
professor at the University of Washington who monitors bird deaths
through Washington, Oregon and California.
That is probably because the near-shore ocean conditions are shifting,
but exactly how is not so clear, she says.
She suspects the deaths are driven by something that’s happening during
the winter, before upwelling usually begins.
Some of the same type of birds were found on Oregon beaches in 1980,
said Range Beyer, an independent researcher in Newport who has compiled
counts of current and past bird deaths along the coast on his Web site,
at http://www.orednet.org/\UNSTRIPrbayer/lincoln/2007-beached.htm. So the
deaths are not entirely unprecedented.
"I sort of view it as we have a large puzzle here," he said. Part of
the mystery is that scientists have limited knowledge of some rarer
species, such as horned puffins, so it is difficult to know how they
behave normally and how current conditions might be changing that.
People who find dead birds on the beach should leave them in place, so
they can be counted in regular beach surveys. Reports can be submitted
online at oregoncoastwatch.org.