After struggling through years of punishing drought, California waterfowl and flocks of migrating birds are now enjoying a rare bounty of water as winter storms and spring snowmelt submerge vast tracts of Central Valley landscape. But even as birders celebrate the return of wet conditions along portions of the Pacific Flyway, experts worry that this liquid bonanza could ultimately poison tens of thousands of the avians as temperatures rise and newly formed lakes and ponds begin to evaporate. The concern: botulism. … [John Carlson, president of the California Wildfowl Association], estimates there is a “high probability” of a die-off this summer. That grim prognosis has added to the emotional whiplash bird lovers and wildlife officials have experienced in recent years as extreme climate variability has gripped the West Coast, alternately parching and starving waterfowl and providing them with a surfeit of habitat.

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