This is a response about the dead birds being found in Elkhorn Slough from Kerstin Wasson, Research Coordinator at the Elkhorn Slough National Estuarine Research Reserve:

It appears that these dead birds are part of a larger event — a lot of cormorants and grebes have been dying of starvation due to lack of anchovy food resources this spring.  Vets have conducted fairly extensive tests and have thus ruled out all diseases that might be expected.  So while sad, this appears to be part of natural cycles of richness and scarcity in the ocean.

Below are links from two recent articles on the subject.