Next time you lift a glass of Gallo wine, you might thank the owls that helped produce it.

E.&J. Gallo Winery of Modesto provides nesting boxes for the raptors to encourage them to prey on rodent pests in vineyards.

This practice reduces pesticide use and is an example of sustainable agriculture, loosely defined as producing food in a way that does not exploit the land or the people who work it.

An increasing number of retailers have been asking suppliers to adopt such practices. The largest, Wal-Mart, this month announced a plan to train a million farmers around the world.

“If you look at the Fortune 500 companies, they are responding to consumer pressures and global pressures for resources,” said Barbara Meister, marketing manager for SureHarvest, a company that provides certification and other services for farmers interested in sustainability. “And they are responding to their stockholders who are asking about how a company is doing in the way of treatment of workers, its carbon emissions and use of water.”