"Be still, be still," the woman next to me whispered urgently.

A dozen binoculars had suddenly shot up, focusing on a brown bird stepping gingerly from the nearby bullrushes. It was a Yuma clapper rail, a threatened species that is rarely seen, making a brief public appearance at La Cienega de Santa Clara, a desert wetland that survives on agricultural runoff from Arizona.

On this cool, cloudless morning, I had joined a group of 17 people touring the Colorado River Delta, an area devastated by decades of diversion upstream. After rattling down a dirt road through a parched brown landscape, La Cienega had at first seemed more dream than reality.

La Cienega has become a key stop on the Pacify Flyway for plovers, sandpipers, dowitchers and other migratory species. Though some 350,000 ducks, geese and other birds annually visit La Cienega, the largest wetland in the Sonoran Desert, few tourists make it to this remote spot some 60 miles from Yuma, Ariz.

But this was not your typical tour. Conceived by the Tucson-based conservation group The Sonoran Institute, the five-day trip was designed to give us a feel for the people and places that make up the Colorado River Delta. The region spans the U.S.-Mexico border, much of it in the Mexican states of Sonora and Baja California.

The tours are operated by the nonprofit La Ruta de Sonora Ecotourism Association, an institute offshoot. The tours allow many overlooked communities to showcase their amenities and provide a source of revenue for residents. Visitors gain unusual insight into local cultures and issues.

From the stark outline of the Cucapa Mountains to the quivering cattails of La Cienega, to birds that congregate on the sloping beach at the fishing village of Golfo de Santa Clara, there is still much beauty to behold in the delta. Splitting our group into two vans, we spent hours traveling to its remotest reaches.

In the vast, flat Mexicali Valley, we drove down straight roads, past sorghum fields with red-wing blackbirds, through small dusty towns with sudden bursts of bougainvillea. If not for an intricate network of canals channeling water from Mexico's allocation of the Colorado River, much of this area would be desert.

La Ruta's tour started north of the border, with stops in Yuma and the nearby Cocopah Indian Reservation. Known as the Cucapa in Mexico, the tribe, which used to guide steamboats up to Yuma through the maze of wetlands and river channels that was the delta, has been split by the border. The Cocopah Nation in the United States operates a casino and is working to restore riparian habitat along the Colorado River.

Once lush with water and wildlife, the delta has shrunk to less than one-tenth its original size. The few remaining natural areas are sustained by agricultural return, and now even those flows are threatened as cities and farms upstream divert every drop. Tour promoters are hoping that bringing eco-tourists to the delta can help preserve and restore key areas by increasing international understanding of water issues and bringing attention and resources to the region's often overlooked communities.

Jo Falls, director of public programs at Tohono Chul Park, a desert preserve in Tucson, was one of the three tour leaders. "This is an effort to introduce people to the Mexico that is beyond border towns," Falls said. Though many want a deeper acquaintance with Mexico, "they just don't know how to go about it."

Shopping meant purchasing beaded jewelry at the small museum in the Mexicali Valley at El Mayor, an impoverished community of some 200 Cucapa Indians, whose ancestors survived by fishing. Dining was often alfresco, such as the sumptuous lunch of beef burritos served at the side of La Cienega by the women of the community known as Ejido Luis Encinas Johnson, with a presentation by ejido president Juan Butron.

He told us he's worried that changes upstream could affect the flow to La Cienega. "The birds would stop coming, and if the birds stop coming, then you'll stop coming," he told us.

At our hotel in the border town of San Luis Rio Colorado, our after-dinner entertainment was a slide show and lecture about the region by Jose Campoy, director of the Upper Gulf of California and Colorado River Delta Biosphere Reserve.

Our group was well traveled, well educated and eager to learn. It included working professionals, but most were retirees, including a former nurse, an archaeologist and an investment banker.

"I see this as the opposite of a cruise," Sandy Woodward said. The retired librarian from Port Angeles, Wash., stepped down a dirt path in Campo Mosqueda, a tourist camp and site of a restoration project on the Rio Hardy, a former Colorado River tributary now fed by treated sewage and agricultural runoff.

Several said they were struck with how hard Mexicans are working at conservation and restoration. "They don't have the resources that we do, but they're expending it in a higher proportion," said Joyce Ryba, a retired biological researcher, also from Port Angeles.

As they head down the two-lane highway to the Gulf of California resort of San Felipe, most tourists take no notice of the Rio Hardy. In the 1950s and '60s, the Rio Hardy was a popular destination for hunters and fishermen from California and Arizona. Many of the Rio Hardy's fishing camps today are all but abandoned as the river has shriveled and salt cedar has invaded its banks.

Some have held on, such as Campo Mosqueda, the largest camp, where we met with members of The Ecological Association of Users of the Hardy and Colorado rivers. They are trying to restore the flow to the river and create a tourist corridor.

"Restoration of the delta is feasible," the Sonoran Institute's Edith Santiago told us. "It just requires modest flows."

For scientists and conservationists, the delta represents nature's resilience: Just add water and even the most maligned ecosystem can rebound. That's what happened in La Cienega. The 40,000-acre wetland surged in the 1970s, when agricultural runoff from the Wellton-Mohawk Irrigation District in Arizona began draining into Mexico. That flow could end if U.S. government water managers decide to keep the water in Arizona, recycling it through the Yuma Desalting Plant.

On this November morning, La Cienega's surface water was like glass as we split into three canoes and two boats with tiny motors. Moving slowly through lagoons and small canals, we spotted terns, yellow-headed blackbirds, ducks, pelicans, coots, snow geese and meadowlarks.

"Look, 12 o'clock," someone said, and we all turned to see a line of black and white against the deep blue sky - Caspian terns flying overhead.

Our guides were members of the Ejido Luis Encinas Johnson, which has built tourist cabins on the site, hoping to entice overnight visitors. La Ruta bought the group its canoes and paddles, and the ejido rents them out to groups such as ours.

My personal paddling instructor was Carmen Christy, a 61-year-old resident of Tucson. Christy, an avid canoeist, has traveled to other parts of the Colorado River and was curious about the lower portion. "I have to see where it all ends up," she told me on that crystal clear morning when anything seemed possible. "Isn't it glorious?"

IF YOU GO

La Ruta de Sonora was established by the Sonoran Institute to promote sustainable tourism in the Sonoran Desert and the Upper Gulf of California.

The five-day Colorado River Delta Tour begins at $1,099, with everything included - transportation from Tucson, meals and hotel accommodations.

La Ruta de Sonora and the San Diego Natural History Museum will jointly lead a Colorado River Delta tour leaving from and returning to San Diego, scheduled for Oct. 23-27.

For more information about the delta tour and other trips, see laruta.org or contact La Ruta directly at information@laruta.org or call 800-806-0766.

Sandra Dibble is a staff writer for The San Diego Union-Tribune.

Visit Copley News Service at www.copleynews.com.