FLOODING RICE FIELDS SUPPORTED : METHOD BRINGS BIRDS TO NORTHERN VALLEY.

Byline: Chris Bowman Scripps-McClatchy Western Service

Flooding - instead of burning - rice fields after harvest appears to be a double environmental blessing for the Sacramento Valley.

The alternative not only spares the air of gritty smoke, but, bird experts now say, it also boosts the number and variety of migratory birds wintering in the basin.

An extensive valley survey released by the University of Nevada, Reno, provides the first scientific backing for growers and duck hunters who tout the November-to-March submersion of rice fields as a way to break down the stubble and restore populations of wintering waterfowl - mallard, teal, pintail and ibis - that blackened the sky before the Gold Rush.

Not surprisingly, UNR researchers found significantly higher densities of waterfowl - six times greater for northern pintail - in the flooded crop land than in fields left dry. The pattern held true for 24 of 30 species observed, one exception being geese.

``It's nice to be able to say, `Yeah, we were pretty much right,' '' said Mike Bias, a biologist with the Sacramento office of Ducks Unlimited, a national conservation and hunters group that helped fund the four-year study.

Bias noted one ``happy surprise'': The farmers' artificial wetlands are attracting many shore birds, including the dunlin long-billed dowitcher and the least sandpiper.

The researchers looked at all kinds of native birds, not just game species, and compared the different flooding and rice straw-disposal methods. The survey of more than 100 fields in Butte, Colusa and Sutter counties spanned four winter migrations, October through March 1993-1996.

Species that benefit most from shallow winter flooding are those that have lost much of their natural wetland habitat to water diversions and agriculture, said Chris Elphick, the lead researcher and a doctoral student in wildlife conservation at UNR.

Although Ducks Unlimited funded a major chunk of the $90,000 study, many of its Northern California members who hunt outside the rice-growing region are not happy with the group's promotion of artificial wetlands.

Duck clubs in natural wetlands such as the Suisun Marsh in Solano County and the Grassland Ecological Area surrounding Los Banos complain that the winter flooding in the valley is luring, or ``short-stopping,'' southbound birds that would otherwise frequent their hunting grounds.

Dave McCabe, who has hunted the private Grassland every autumn for the past 40 years, says the rice farmers' habitat expansion efforts are misguided and are responsible for a recent decline in Grassland hunting success during the latter half of the duck season, late November through December.

``It's apt to concentrate and hold large numbers of waterfowl and preclude them from traveling south,'' said McCabe, who is on the board of directors of the Grassland Resource Conservation District.

McCabe said the well-being of the 160,000-acre Grassland is directly dependent on hunters who collectively own 70 percent of the refuge and pay for irrigation and other improvement to keep the area attractive to waterfowl. Members of Grassland duck clubs pay initiation fees of $35,000 to $55,000 plus an annual charge of $30 to $80 per acre, he said.

``The winter flooding is happening at the expense of the more diverse and natural wetlands,'' McCabe said. ``You are basically creating a monoculture.''

Elphick acknowledges that flooded rice fields as a foraging habitat are inferior to natural wetlands. Nonetheless, he said, ``they play a major role in maintaining water-bird populations in the Central Valley.''