MARYSVILLE – When birds and farmers come together, it is often a matter of conflicting goals. However, a steady evolution in the interaction between rice farmers and birds has been changing that equation in the northern Sacramento Valley.

Nowhere is that more evident than along a stretch of Woodruff Road outside Marysville, where large rice dryers tower over the landscape.

The 23,000 acres of rice fields that surround the dryers were recently harvested, and now sit under inches of water. And nesting amid the mire are some of the most majestic of all birds: tundra swans. The elegant white-feathered birds, which summer in Alaska, have taken to gracing the flooded rice fields as their winter home.

As the Central Valley wetlands that once allowed the swans to feast on submerged vegetation and organisms disappeared, the swans moved to the flooded grain fields.

Rice farmers flood after fall harvest primarily to encourage leftover rice stalks to decompose. Since the 1990s, the practice has largely superseded burning the stubble, which was phased out because of air quality issues.

The flooding that replaced it immediately attracted a variety of birds, and a number of benefits have come from that. The fields are widely used by duck hunting clubs, for instance, and farmers get free fertilizer from hosting thousands of birds.

Ecotourism is another offshoot. For birders, the flooded fields create a landscape where birds can be viewed at very close range.

Most Saturdays from now until the end of January, the state Department of Fish and Game offers tundra swan tours. As many as 30 people participate in each tour, which consists of a caravan of vehicles to viewing locations north of Marysville, said Brian Gilmore, an interpretive scientist with Fish and Game and a tour leader.

In addition to one of the largest seasonal concentrations of tundra swans in the region, tours allow viewing of other species, including ducks, geese, ibises, herons and egrets.

The tours have the blessing of Charles Mathews, whose family has farmed rice in Marysville since the 1970s. Mathews is keen on flooding some of the 6,000 acres he farms for himself and other landowners so that birds can winter on the land.

"People forget that, in this case, the farmer is the environmentalist," said Mathews. "Without rice farming there would be almost 400,000 acres that would not flood."

Mathews said he floods fields in spring to grow the rice. Fields are drained at the end of August, and harvesting begins in mid-September. Fields are flooded again in November to help decompose the straw.

About 90 percent of the winter activity on the land he farms is duck hunting, which increases the value of most rice farm properties, Mathews said. Once duck season ends in January, Mathews keeps his fields flooded at least until late February.

"It costs us another $15 an acre to irrigate the land and maintain it throughout most of the year," said Mathews.

Almost all rice farming in the Central Valley is north of Sacramento; the valley is the third largest rice-producing region in the United States.

Between 1939 and 1985, rice acreage jumped 52 percent in the Central Valley, according to statistics on Calrice.org, the California Rice Commission website.

After stubble burning was mostly phased out in 1991, flooding increased dramatically. Flooded fields grew from 60,000 acres in the 1980s to 270,000 acres in 2007, according to U.S. Fish and Wildlife Service data.

The burning ban, coupled with use by duck clubs and concern about shrinking winter bird habitat, has put rice farmers in a curious category within the agricultural community.

"The rice industry was way ahead of the game and set the standards for finding common ground with the environmental community," said James Hill, agronomist in the Plant Sciences department at UC Davis.

Hill said 40 to 50 percent of rice acreage is now flooded in the Central Valley. "The goal is not to flood all the rice fields … as waterfowl and shorebirds prefer different habitats. The ideal is a patchwork."

Over time, the largest benefit from the flooding of rice fields may be not increased farm values due to duck hunting, but the influx of dollars from ecotourism, said Bruce Forman of Fish and Game.

Forman said a 2011 survey of fishing, hunting and wildlife-associated recreation makes the case that ecotourism is a bright spot for places like Marysville.

In that national survey, expenditures for wildlife viewing activity in the state totaled nearly $3 billion last year, as opposed to just under $1 billion for hunting activity.

TUNDRA SWAN TOURS

What: Co-hosted by local rice farmers and the Department of Fish and Game, the tours will focus on tundra swans in a premier location for viewing. Binoculars will be available.

When: 9:30 to 11:30 a.m. and 1 to 3 p.m. Saturdays through Feb. 2

Where: Yuba County rice fields north of Marysville

Cost: $7 donation; preregistration required.

Information: (916) 358-2900; www.dfg.ca.gov/regions/2/SwanTours

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