Since 2014, US farmers have been deliberately flooding their fields to create habitat for migratory birds; a decade later, 180,000 acres of farmland have become temporary wetlands serving as vital habitat for millions of birds

The Pacific Flyway stretches for more than 4,000 miles along the western edge of North America, forming one of four major migration routes used by birds on their seasonal journeys. Around one billion birds travel along the flyway each year, making the wetlands, lakes and other habitats scattered along the route vital stopover points.

But some of those places to stop have been disappearing. In California’s Central Valley, one of the flyway’s important stopover regions, about 95% of the historical wetlands have been lost, primarily to agriculture, according to the conservation organization Ducks Unlimited. For birds that have already traveled thousands of miles, and still have thousands more to go, the shrinking supply of suitable habitat can turn migration into a race between exhaustion and survival.