A bird is cleaned at the International Bird Rescue in Fairfield, California January 20, 2015. A gooey, unknown material discovered on the eastern shores of San Francisco Bay is clinging to the feathers of birds, and more than 100 birds, mostly species of oceangoing, diving ducks, have died after their feathers were fouled by the viscous substance now undergoing testing at state labs in Sacramento. (Photo by Robert Galbraith/Reuters)

A bird is cleaned at the International Bird Rescue in Fairfield, California January 20, 2015. (Photo by Robert Galbraith/Reuters)

A horned grebe is washed at International Bird Rescue, Tuesday, January 20, 2015, in Fairfield, Calif. The death of 100 birds in the San Francisco Bay Area has baffled wildlife officials who say the feathers of the birds were coated with a mysterious substance that looks and feels like rubber cement. (Photo by Marcio Jose Sanchez/AP Photo)

A male surf scoter, left, and female surf scoter interact after being treated, washed and dried at International Bird Rescue, Tuesday, January 20, 2015, in Fairfield, Calif. (Photo by Marcio Jose Sanchez/AP Photo)

Workers clean a bird at the International Bird Rescue in Fairfield, California January 20, 2015. (Photo by Robert Galbraith/Reuters)

Workers clean a bird at the International Bird Rescue in Fairfield, California January 20, 2015. (Photo by Robert Galbraith/Reuters)

A worker carries a bird at the International Bird Rescue in Fairfield, California January 20, 2015. (Photo by Robert Galbraith/Reuters)

A bird is cleaned at the International Bird Rescue in Fairfield, California January 20, 2015. (Photo by Robert Galbraith/Reuters)

A bird is cleaned at the International Bird Rescue in Fairfield, California January 20, 2015. (Photo by Robert Galbraith/Reuters)

Workers clean a bird at the International Bird Rescue in Fairfield, California January 20, 2015. (Photo by Robert Galbraith/Reuters)

A volunteer checks on a bird after it was cleaned at the International Bird Rescue in Fairfield, California January 20, 2015. (Photo by Robert Galbraith/Reuters)

A volunteer feeds a bird after it was cleaned at the International Bird Rescue in Fairfield, California January 20, 2015. (Photo by Robert Galbraith/Reuters)

A worker checks on birds being dried after a cleaning at the International Bird Rescue in Fairfield, California January 20, 2015. (Photo by Robert Galbraith/Reuters)