California Department of Fish and Wildlife
This article was originally printed in Outdoor California magazine, July - August 2001.
Subscribe to Outdoor California

Hill Slough Wildlife Area: Linked to the Past... Heading into the Future

By Ronald D. Rogers

Hill Slough Wildlife Area, located in the northern part of the Suisun Marsh in Solano County, is part of a complex of Department of Fish and Game (DFG) lands that include Grizzly Island Wildlife Area and Peytonia Slough Ecological Reserve. Suisun Marsh is the largest contiguous estuarine marsh in the United States. It is known for its importance as nesting and wintering habitat for Pacific Flyway waterfowl and shorebirds, as well as habitat for many sensitive, threatened and endangered fish, birds, mammals, and plants. It is also a unique site because of its close proximity to the cities of Fairfield and Suisun.

The first acquisition of 1,100 acres in 1978 made Hill Slough an official state wildlife area. Subsequent acquisitions and donations have expanded the site to its current size of 1,750 acres. Originally, Hill Slough, a relatively small wildlife area, was acquired to meet mandates of the state's Suisun Marsh Preservation Act of 1977. Though small in size, its importance has grown immeasurably as it will be the site of a 200-acre pilot project to convert diked wetlands into tidal wetlands and a study area to learn more about several sensitive animal and plant species. The project site is currently in the planning stages.

Additional lands are also being considered for acquisition. A 250-acre parcel at the upper-most reaches of Hill Slough, formerly used as a duck hunting club, would also be returned to tidal marsh if acquired. Another 20 acre parcel a little further to the east was developed by Solano Garbage Company as a tidal marsh and upland transition area as mitigation for the company's nearby road project. This parcel will eventually be transferred to the DFG. Tidal wetland development is not the only activity at Hill Slough.

Recreational angling is the number one public use at Hill Slough, and more than 10,000 anglers use Hill Slough annually. A one-mile drive or bike ride from Highway 12 down Grizzly Island Road gets you to the parking area. There is no vehicle access but the entire area is open for walk-in trips. Anglers spread out for a half mile or so east or west from the parking area to try for striped bass or catfish in Hill Slough. A one-mile walk to the west takes you to the mouth of Hill Slough at Suisun Slough.

Bird watching, hiking, and sight-seeing are other popular uses that attract visitors to Hill Slough. During the fall, winter, and early spring, 550 acres of managed ponds are flooded to provide habitat and sanctuary for several thousand migratory waterfowl and shorebirds. Including Hill Slough, the DFG manages five sanctuaries in the Suisun Marsh, consisting of approximately 3,500 total acres, during the annual waterfowl hunting seasons. Other viewing opportunities are of wintering raptors, such as ferruginous and rough-legged hawks, which join the year-round residents such as golden eagles, northern harriers, and red-tailed hawks working the ponds and uplands for food. For visitors who just want to get out and hike in an area dedicated to wildlife and see what nature has to offer, Hill Slough has several miles of levees that are easily accessible and walkable.

Over the last few years, students from the University of California at Davis have been studying an endangered marsh plant called soft-haired bird's beak. There are only a few populations of this plant in and around the Suisun Marsh. Researchers are hoping to find ways to protect and enhance these existing plant populations and to develop the habitat in a manner conducive to growing new populations of soft-haired bird's beak.

In addition to the sensitive plants, wintering waterfowl, shorebirds and hawks, Hill Slough is home to a few other threatened and endangered wildlife. The California clapper rail and California black rail are found in the tule and cattail areas along many of the sloughs. The salt-marsh harvest mouse and Suisun shrew are found in the high marsh and managed ponds dominated by dense stands of pickleweed. Pickleweed is a salt tolerant plant that thrives in the brackish (partly salty) water and soil conditions in the Suisun Marsh. Two areas with a total of 300 acres are specifically managed intensively on Hill Slough to produce habitat for the salt-marsh harvest mouse and Suisun shrew.

One of the biggest challenges for DFG managers at Hill Slough is to maintain a balance between public use and the needs of the area's wildlife. Too much hiking along the levees can increase disturbance and decrease the value of the ponds as sanctuary for waterfowl. This same type of disturbance can occur where the rails are found. Rails are particularly sensitive during courting and nesting season which lasts for several months in the spring and summer. Although public use is high and Hill Slough is adjacent to housing developments and freeways, DFG has maintained the balance and disturbance of the wildlife has been minimal.

As part of balancing wildlife and human needs, the most ambitious project at Hill Slough is a proposed Pacific Flyway Interpretive Center. A local committee has been involved in the planning of this center for many years. The plan envisions a museum, classrooms and trails where local school classes as well as the daily visitor can study and learn more about marshes, pond management, fish and wildlife, and the Suisun Marsh. The facility will tell the history of the Suisun Marsh, including the values and uses as a hunting area from the time before settlers arrived to the modern era.

Although Hill Slough Wildlife Area will see some changes in the future - links to the past as a waterfowl sanctuary and sensitive species habitat will be maintained and improved where possible.

Hill Slough is immediately adjacent to city limits of Suisun City and is also just south of Highway 12, which is the east-west artery between Fairfield and Rio Vista. For additional information, call (707) 944-5500.