A large flock of Snow Geese takes flight from a field next to Garmier Road near Tisdale Weir in Sutter County, California. Kenneth James / DWR

INSIDE CLIMATE NEWS: California rice fields offer threatened migratory waterbirds a lifeline

Conservation groups are working with Central Valley farmers to restore critical habitat for wetland birds struggling to subsist on a fraction of their historic wintering grounds. But finding the right spots is challenging.

By Liza Gross, Inside Climate News

This article originally appeared on Inside Climate News, a nonprofit, non-partisan news organization that covers climate, energy and the environment. Sign up for their newsletter here.

On a misty December morning, a few dozen sandhill cranes stood in shallow water in the middle of a flooded rice field in the Sacramento Valley, about 90 miles north of San Francisco. The cranes, statuesque wading birds with a long, elegant neck and broad wings, appeared remarkably still for a gregarious species known for their dramatic dance moves.

Sandhill cranes jump several feet in the air as they kick their lanky legs helter-skelter, bow their heads and flap wings that span six to seven feet in a spectacular display associated with courtship and bonding between mated pairs. But the birds in the middle of the field did not even move. They were decoys, made of plastic. Still, they fooled one ecologist, from a distance at least.

More importantly, the decoys, aided by recordings of the crane’s otherworldly squawks—described by legendary conservationist Aldo Leopold as the “trumpet in the orchestra of evolution”—attracted a few flesh-and-blood birds to their side. It was a good sign for ecologists working to create new roost sites for species that need every inch of habitat they can get.

Sandhill cranes. Photo by DWR.

Sandhill cranes return to the same spots every year, so seeing some birds roosting with the decoys is “very exciting,” said Greg Golet, an avian ecologist with The Nature Conservancy who helps run a program to expand wetland habitat for migratory species called Bird Returns.

The Central Valley is one of the most important regions of the Pacific Flyway for cranes and other waterbirds to overwinter or rest and refuel on their way further south. It supports hundreds of resident and migratory species that come here from breeding grounds as far north as the Arctic tundra.

Migratory birds evolved over millennia to depend on the food-rich habitat provided by the vast expanse of both permanent and seasonal wetlands that once stretched hundreds of miles from the Sacramento Valley in the north to the Tulare Basin in the south. It took little more than a century after California became a state in 1850 for urban and agricultural development, supported by a massive irrigation and flood control network, to drain more than 90 percent of the valley’s wetlands.

Protecting wild birds and the vanishing native ecosystems they depend on has left ecologists scrambling to create as much habitat as possible, where and when migrating birds need it most.

Toward that end, Bird Returns, part of the Migratory Bird Conservation Partnership between The Nature Conservancy, Audubon California and Point Blue Conservation Science, offers farmers incentives to adopt practices that support the birds’ foraging and roosting needs on agricultural fields that replaced wetlands.

Bird Returns uses funds provided by the California Department of Fish and Wildlife to pay farmers to flood their fields during critical migration periods, said Andrea Jones, Audubon California conservation director. “In spring and fall, we put out a bid to farmers and duck club owners to flood fields when shorebirds are coming to the Central Valley and are looking everywhere for water,” Jones said. “We’ve flooded tens of thousands of acres over the last two years that way.”

During that time, Bird Returns created a program to meet the special needs of greater sandhill cranes, which are found primarily in the Sacramento Valley and the Sacramento-San Joaquin Delta to the south.

Greater sandhills are a California-listed threatened species while their cousins, the lesser sandhills, are a species of special concern. The shorebirds that share this once expansive wetland habitat with cranes and scores of other species are among the fastest declining groups of birds on the planet.

A warming world is likely to worsen the birds’ already tenuous conditions, as droughts become more frequent and intense, leaving less water for wetlands and forcing birds into smaller and smaller patches where diseases like avian flu can easily spread.

Birds in flooded rice fields in Yuba County. Photo by DWR

Changing Old Habits with New Habitats

Back at the decoy site, Billy Abbott tended to a jerry-rigged sound system sitting at the edge of a narrow stretch of dirt separating two flooded fields a few hundred feet from the plastic cranes. The system, though crude, holds all the equipment needed to broadcast crane calls for about three hours after dawn and then again around dusk as part of a “social attraction” gambit. The calls, recorded along the Pacific Flyway, aim to lure cranes to the site by recreating the soundtrack of their daily routine, as they fly out to forage in the morning and return to the roost site to sleep at night.

“There’s a lot of noise at crane sites, so this is mimicking that natural pattern,” said Abbott, a Nature Conservancy avian field scientist. Abbott turned on an MP3 player tucked in a box, filling the air with the cranes’ loud, bugle-like calls, which are as distinctive as their dance. “Hopefully, the combination of the decoys and the calls can pull them in.”

Cranes need nighttime roosting sites flooded to a depth of about 3 to 9 inches, so they can easily hear or feel predators moving through the water. From their roosts, they typically fly no more than 3 miles to feed, so foraging sites need to be nearby.

Farmers who work with the program flood their fields to the appropriate depth for roosting or provide foraging sites by leaving harvested rice or corn fields untilled, so cranes can access the leftover grain.

A large flock of Snow Geese takes flight from a field next to Garmier Road near Tisdale Weir in Sutter County, California. Photo taken January 12, 2023.
Kenneth James / California Department of Water Resources.

Some of the densest crane roosts are found in the Delta, about 90 miles southeast of the social attraction site near Arbuckle. Yet the peat-rich soil in the region is rapidly subsiding, as exposure to oxygen decomposes the soil and releases carbon dioxide. Subsiding land, combined with sea level rise and ongoing loss of habitat to urban and agricultural development, will only get worse as global temperatures rise, experts say.

Maintaining Central Valley crane populations could depend on creating or restoring their habitat in new areas, scientists with Point Blue Conservation Science warned in a 2017 white paper.

The team recommended expanding crane habitat to build resilience to sea level rise, so if birds lose one important wintering area, they can go somewhere else, said Bobby Walsh, an avian ecologist who joined Point Blue after the study. Helping cranes move away from wintering sites prone to sea level rise is one of the goals of the decoys, he said.

Staten Island, a crane hotspot in the Delta, has already subsided as much as 30 feet, The Nature Conservancy’s Golet said. “And that whole island could be gone as a foraging and roosting site for the cranes.”

There’s not enough space immediately surrounding that area, so Golet and his colleagues have tried to find more resilient sites in the Sacramento Valley. The valley has tremendous potential given how much irrigation infrastructure is built into the landscape, he said. Yet simply creating habitat is no guarantee cranes will take advantage of it.

The birds tend to return to the same site year after year, said Golet. “The trick is getting the cranes to spread out.”

That means the team has to not only identify sites that suit the birds’ needs but also encourage these creatures of habit to change their routines.

Cranes, among the oldest living bird species, adopted that routine somewhere along their 2.5-million-year evolutionary history. Since cranes fly only a short distance from their roost sites to forage, the team has focused on creating new places to roost at the edge of their foraging range. Several years’ worth of roosting site observations suggest that cranes seem willing to go to a nearby site if the old one isn’t flooded that winter for whatever reason.

And it looks like they might be willing to try a new site if they think it’s already occupied. So far, Golet’s team has seen a few cranes roosting alongside the plastic decoys on two different occasions. They may see more when they pull images from a camera that snaps photos every hour.

Seeing even a few cranes at a new roosting site is good news, said Golet. “It suggests that we may be on the right track in helping them expand their foraging range to take advantage of the high-quality habitats we are providing with the growers.”

He’s also been encouraged to see that what’s good for cranes is good for other waterbirds. “Tons of birds use the flooded landscape,” Golet said. “And there’s a lot that use these dry fields as well because they have food.”

Tundra swans, Sutter County by Cheryl and Glen

Vanishing Shorebirds

Tens of thousands of Ross’s geese, snow geese, swans and ducks crowded into a flooded rice field along a Sacramento Valley country road one day last month, chattering loud enough as they jostled for a spot among the throngs to drown out the occasional passing truck.

Yet these immense flocks represent a tiny fraction of the historical populations that relied on the wetlands before agricultural and urban development, said Abbott. “Estimates before the 1850s were 50 to 80 million birds.”

Within a century, federal and state water engineering projects had turned millions of acres of living wetlands into one of the most highly managed water systems in the world.

People see these giant flocks of birds in the winter, like the geese out there, said Golet, pointing to the flooded field, and think they’re all doing great. But different migratory species arrive and leave at different times, he said, and the reality is that the needs of species like shorebirds aren’t well matched to how the land is managed.

Shorebirds start showing up in July and August and many come back later in spring, particularly the species that stop here on their way from Alaska or the Arctic to South America. The valley is way less hospitable to these species during these shoulder seasons, he said.

There’s typically a lot of flooded habitat out here in the winter, and that works well, Golet said, particularly for waterfowl and rice agriculture, because farmers flood fields to decompose the stubble. But traditionally, fields aren’t flooded when shorebirds are coming from the south because rice is still growing, or when they’re heading north because farmers have to till the fields in preparation for planting.

This highly engineered water management system bears no resemblance to the natural patterns of water distribution and abundance shorebirds and other species adapted to over millennia. That’s why even really wet years don’t help shorebirds, Golet and his colleagues discovered in a 2022 peer-reviewed study. Shorebirds need habitat flush with crustaceans, insects and other invertebrates during early fall and late spring. But conditions were just as bad for them during dry and wet years, the team reported, because water allocations in the valley are designed to meet human demands, not to help birds cope with the loss of the resources they evolved to depend on.

Maintaining partnerships with farmers is critical for shorebirds, said Aududon’s Jones. With so little of the Central Valley protected as conservation land and human development showing no sign of slowing, rotational crop fields can provide essential habitat for rapidly declining species that migrate thousands of miles.

“Birds can move around the landscape, but they still need enough food,” said Jones. “How healthy are the birds that stop here? Do they have the fat they need to make their long journey?”

Such concerns keep Jones up at night. “The last thing you want is for them to stop in the Central Valley and leave hungry,” she said.

In addition to flooding their fields for waterfowl, some rice farmers have hunting blinds that they lease to hunters for anywhere from $3,000 to $8,000 per season, said Dan Smith, a waterfowl scientist with Ducks Unlimited’s western region. About 30 percent of California waterfowl hunters hunt primarily in flooded rice fields, he said.

Typically, there are about 300,000 to 350,000 acres flooded by December, but Smith thinks that acreage dropped by about half during the last drought. When flooded rice acres drop below 300,000, he said, waterfowl managers worry that populations won’t find enough to eat.

“Birds can move around the landscape, but they still need enough food … The last thing you want is for them to stop in the Central Valley and leave hungry.”

— Andrea Jones, Audubon California conservation director

Fields flooded to a depth that attracts ducks are too deep for shorebirds, which typically probe the mud for food with their bills. And because cranes avoid hunted areas, the new program on cranes excludes fields where hunting occurs.

Conservation organizations have found other funding sources to compensate farmers who might otherwise support duck hunting to supplement their incomes. With funding from the state wildlife agency, Bird Returns can draw on more than a million dollars to pay farmers to enroll in the crane and shorebird program.

Both programs have been very successful, Golet said. And even though farmers lose that income from hunting clubs, “we’ve still had lots of people sign up for the program,” he said. “I think that bodes well for the future.”