What Does It Mean When Animals Suffer a Vast Die-Off?

Are die-offs occurring more often?  To the casual reader, it can certainly seem that reports emerge on a regular basis of thousands of animals of a species suddenly dying.  The latest victims are common murres in the Northeast Pacific. They have been dying for months, but estimates of the toll jumped sharply when David Irons, a retired United States Fish and Wildlife Service biologist walking a beach in Whittier, Alaska, found close to 8,000 dead birds in early January.

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