It’s a hot, mid-summer day but a welcome breeze keeps a team of bird conservationists cool as they walk along an earthen levee in Suisun Marsh, a flat expanse between San Francisco Bay and the Delta. … The team is here to track the effectiveness of a program called BirdReturns, which helps birds in California’s vast Central Valley. … But the Central Valley has lost 95% of the wetlands where migrating birds once rested and refueled. BirdReturns pays farmers and wetland managers to flood strategic points during the late spring through early fall dry season, providing temporary wetlands when and where birds need them. … Now BirdReturns has expanded to include Suisun Marsh duck clubs, which account for about half of this 115,000-acre managed wetland.