By Ben Ikenson

The wetlands of the Sacramento National Wildlife Refuge Complex provide crucial foraging and roosting habitat for migratory birds along the Pacific Flyway, but prolonged drought has made resource management there more difficult.

The complex, in California’s Central Valley, consists of five national wildlife refuges (Sacramento, Delevan, Colusa, Sutter and Sacramento River) and three wildlife management areas (Willow Creek-Lurline, Butte Sink and North Central Valley). Collectively, the 70,000 acres of wetlands on these lands represent some of the most intensively managed in the Refuge System. They offer a diversity of wetland habitats with a variety of water depths and vegetation along the Pacific Flyway, which extends from Central and South America to the Arctic.

These U.S. Fish and Wildlife Service wetlands are located near the center of the flyway near other wetlands managed by the state of California and more than 500,000 acres of rice fields. Together, they attract high densities of migrating and wintering waterfowl such as northern pintail ducks, greater white-fronted geese and snow geese, as well as other wetland-dependent species such as tricolored blackbirds, white-faced ibises and giant garter snakes.

However, the drought that has parched California and much of the West for four years has taken a toll.

“We’ve seen vegetation changes to more invasive plant species and anticipate the trend to continue if the drought persists,” says Sacramento Refuge manager Steve Emmons. “The longer the drought lasts, the worse the changes will be and the longer it will take for the habitat to recover when the drought is over.”

Emmons hopes that by spring the snowpack in the Sierra Nevada will melt and restore area reservoirs. (Lake Shasta was at 30 percent of its capacity in early February, according to the complex website.)

Meanwhile, migratory birds continue to benefit from the refuges and wildlife management areas, thanks to coordination among different Service programs and help from partners, including other refuges, federal and state agencies, and non-governmental organizations such as Ducks Unlimited and California Audubon. Water conservation and native grass restoration, a necessity that coincides with drought, have been the primary focus.

“We’ve become very strategic in terms of our water usage and management of our water timing,” says Emmons. “We typically flood wetland units in early fall but have been delaying flood-up and conserving water in other ways to maximize refuge wetland acres flooded over the last two years of the drought.”

While staff members have been able to use water conserved early in the season for later purposes to support migratory bird populations, Emmons says that “we have seen some reduction in the bird numbers on the refuges during this time, primarily a result of less-flooded agricultural fields in the surrounding area, which normally provide much of the foraging habitat for the area’s waterfowl.”

The complex also conducts mowing, disking, spraying and controlled burns. This discourages the spread of undesirable invasive and non-native vegetation, which can more easily out-compete native vegetation in times of drought, and encourages vegetation that benefits migratory birds. Specifically, the complex manages for smartweed, alkali bullrush, tuberous bulrush and swamp Timothy — some or all of which provide food for ducks, geese and other birds.

“The complex has been especially important in providing wetland foraging and roosting habitat that has been in short supply across the landscape,” says Emmons. “It’s also been important in providing food and spreading the birds out to prevent disease outbreaks.”

A wet spring wouldn’t hurt, either.

Ben Ikenson is a New Mexico-based freelance writer.