As federal officials grapple with how to contain the highly contagious strain of avian flu that has infected chickens, turkeys, and dairy cattle on farms across the U.S., a number of scientists are pointing to one factor that could be driving the spread of its virus and its spillover from wild birds to farm animals. Waterfowl—ducks, geese, and swans—are the primary host of the viruses, and large animal agriculture facilities are often found in close proximity to their remaining wetland habitats. For instance, California’s Central Valley and the East Coast’s Delmarva Peninsula are both critical wintering grounds for waterfowl, along major North American bird migration routes, and epicenters of U.S. poultry production. As a result, some scientists who track waterfowl question whether this geographic overlap—alongside the shrinkage of waterfowl habitats—creates more opportunities for the virus to spread between infected waterfowl and the animals in agricultural facilities.

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• Napa Valley Register: Napa wetlands