This is not an anomaly.

Water shortage causes avian cholera outbreak, killing 10,000 migrating birds

More than 10,000 migrating birds have died this year in Oregon and California from an avian cholera outbreak caused by water shortages in the Lower Klamath National Wildlife Refuge.

The U.S. Fish and Wildlife Service estimates that the death toll could end up being as high as 20,000 birds in the coming months.

Read full story here: http://thinkprogress.org/climate/2012/04/18/466537/water-shortages-cause-cholera-outbreak-killing-10000-migrating-birds-in-klamath-refuge/?mobile=nc