ASTORIA, Ore. (AP) - Horned puffins, mottled petrels and thick-billed murres are seabirds that generally stay far offshore and away from Oregon.

But the birds have been washing up dead on Oregon shores in unusually high numbers this year. People who have discovered them say the birds were starving.

The die-off is a mystery. But theories range from global warming to a scarcity of the herring the birds usually feed on this time of year.

Young herring thrive in colder water. A research fisheries biologist, Bob Emmett, says their smaller numbers could be tied to warm ocean conditions over recent years.

When herring do well, seabirds and salmon often do well, too. But when they do not, Emmett says, the other species don't, either.

Other researchers say the marine system is too complicated to blame the bird deaths on a single cause.

(Copyright 2007 by The Associated Press. All Rights Reserved.)