Chaparral and Oak Woodlands

In Sutter County, chaparral and oak woodland habitats occur primarily on the Sutter Buttes. Both communities occur widely and separately in the foothills on both sides of the Central Valley, although within the Buttes these two communities combine to create a complex patchwork. The two communities, however, are quite distinct from each other in their species composition. The Buttes support a chaparral type without chamise or buckeye, which are often common plants in other chaparral communities. The Buttes chaparral type, designated as Interior Live Oak Chaparral (Holland Element Code #37A00), is dominated by coffeeberry, northern redbud, toyon, scrub oak, poison oak, California bay, and manzanita (Anderson, 1983, 1993). Birds forage in the chaparral community on seeds, fruits, and insects and also find habitat for nesting and roosting. Small rodents and rabbits also inhabit this community, browsing on twigs and leaves and finding shade under the shrubs. The Marysville kangaroo rat is a special status animal that has been recorded in this community. The Sagebrush lizard has also been observed here, 40 miles from its closest range (Anderson, 1983). The chaparral also provides potential habitat for Colusa layia, a special status plant recorded on the Buttes (CDFG, 1993).

The oak woodland type that occurs on the Buttes is designated Interior Live Oak Woodland (Holland Element Code #71150). The species composition includes interior live oak, blue oak, occasional valley oak and oracle oak (a hybrid of interior live oak and black oak). Valley oak is a California special status species. These woodlands provide important habitat for many birds, for both nesting and acorn and insect foraging. Oaks are also used by many mammals. Deer browse and rest in the shade and other smaller mammals feed on acorns, leaves, and invertebrates. Special status wildlife species known to occur in oak woodlands in Sutter County include San Joaquin pocket mouse, nesting Swainson's hawk, golden eagle, and northern loggerhead shrike.

Non-native (Annual) Grassland

The Non-native Grassland community type (Holland Element Code #42200) is very widespread in the valleys and foothills of California, and is composed largely of low-growing annual grasses and forbs. Because the grass species did not evolve here, the community type is termed by botanists "non-native." The grasses were introduced to California for livestock forage and spread quickly. This upland community type is perpetuated by livestock grazing. The non-native grassland communities in Sutter County extend over portions of the Sutter Buttes, between areas of oak woodland and chaparral, and exist in many smaller patches in other parts of the County among agricultural fields and within undeveloped portions of urban areas. Vernal pools, described under Off-channel Wetlands, occur within this community in small natural depressions with an underlying hardpan layer. The grassland community is dominated by grass species such as wild oats, soft chess, ripgut brome, foxtail barley, and Italian ryegrass, and annual forbs ("wildflowers"), including California poppy, lupine, tidy tips, owls clover, storksbill, and many others.

Grasslands produce large numbers of seeds, an important and reliable food source for numerous seed-eating birds. Raptors cruise the grasslands for preying on these birds and small mammals. Mammals relying on grassland communities include both species that forage on seeds and leaves and carnivores that prey on them. Some mammals construct burrows or dens that, when abandoned, are used by birds such as the burrowing owl or certain reptiles and amphibians. Only a few species of reptiles and amphibians are found in grasslands, because the low structural diversity, that is the "sameness" of the area, provides few sources of refuge other than mammal burrows.

Special status bird species that forage or hunt in grassland habitats include golden eagle, tricolored blackbird, short-eared owl, ferruginous hawk, Swainson's hawk, northern harrier, black-shouldered kite, merlin, prairie falcon, northern loggerhead shrike, greater sandhill crane, and long-billed curlew. Burrowing owl is a special status bird that nests as well as hunts in grasslands. One special status reptile, the coast horned lizard, has potential to occur in Sutter County grasslands. Special status plant species that may occur in this community include veiny monardella, Hartweg's golden sunburst, Ferris's milk-vetch, toad rush, Colusa layia, and trichocoronis.

Agricultural Plant Communities

Although natural communities provide the highest values to waterfowl and wildlife, agricultural communities have become important to numerous wildlife species in the Central Valley. Flooded rice fields, for example, are an important substitute for the native wetland habitats of the state and federally threatened giant garter snake. Harvested rice and corn fields provide important foraging areas to migratory waterfowl in the Central Valley. Row crops with value to wildlife and waterfowl include irrigated pasture and grains like wheat, barley, oats, and alfalfa. Remaining crop types, such as other row crops, orchards and vineyards, generally provide low wildlife habitat values.
Agricultural lands are generally not as useful to mammals, reptiles, and amphibians as they are to birds. Deer, for example, require both a reliable food supply and cover from the elements and from predators within their home range, as well as habitat for rutting and fawning. These requirements limit the availability of suitable habitat. Agricultural fields generally do not provide the different structural components needed for large herbivores, as they usually consist of monocrops of a uniform height. Neither is the necessary food diversity generally available in natural communities, such as bark, diverse foliage, berries, etc. These mammals do make use of agricultural land when traveling from one natural community to another or when under heavy environmental stress. Small mammals, such as rabbits and rodents, forage on the leaves or roots of crops, and in turn may attract small predators such as hawks or feral cats. Other mammalian species known to use agricultural areas include coyote, raccoon, skunks, opossum, and river otters.

Special status bird species that forage in agricultural lands include tricolored blackbird, Swainson's hawk, black-shouldered kite, merlin, greater sandhill crane, California gull, long-billed curlew, and Aleutian Canada goose. California horned lark may also nest in pasture lands.

Rice

Rice fields have partially replaced the role wetland communities once played in the natural ecosystems of the Central Valley. In fact, harvested rice fields and corn fields are the primary agricultural lands used by wintering waterfowl in the Central Valley (Heitmeyer, 1989). Depending on the extent of surrounding natural vegetation and vegetation diversity, irrigated rice lands are capable of providing high wildlife value for several resident bird species. Rice fields have also become an important substitute for the natural habitat of the state and federally threatened giant garter snake. However, irrigated rice lands are of limited value for most terrestrial wildlife species, such as small mammals, because these areas are inundated during much of the spring and summer activity periods of these species.

Vegetated drainage canals, natural drainages, and rice field/levee boundaries, especially those that support dense stands of cattails, tules, blackberries, willows, and cottonwoods, provide substantial value to local wildlife by increasing habitat diversity, plant species composition, and good cover. This habitat was previously described in Natural Rivers or Stream Channels and Man-made Channels.

From season to season, rice fields support a changing variety of wildlife species. During spring planting the fields are flooded, attracting great blue herons, great and snowy egrets, white-faced ibis, raccoons, and sometimes river otters. These species forage on aquatic insects, crustaceans, clams, and snails that inhabit flooded rice lands. Other species that use rice fields throughout the summer months include teal, mourning dove, swallows, black tern, black-necked stilt, American bittern, killdeer, red-winged blackbird, and opossum.

Rice fields typically remain flooded until the fall harvest (around early September). During harvest, snow geese, Ross's geese, Canada geese, greater white-fronted geese (tule geese), and tundra swans customarily begin arriving for winter in the Sacramento Valley (Heitmeyer, et al. 1989). These species and other waterfowl forage on rice, aquatic insects, and succulent aquatic plant species, such as watercress, which commonly grow in rice fields. Diving ducks, such as redhead, scaup, ruddy duck, and bufflehead, do not feed on crops as frequently as dabbling ducks, such as mallards, pintails, and widgeon, as they are awkward on land and are more vulnerable to predation. Diving ducks will, however, use deeply flooded rice fields. During the winter, after the rice fields have been harvested and more waste grain is available, the abundance of small mammals in rice lands increases, resulting in an increased number of foraging hawks.

Orchards

Individual orchards are typically dominated by a single horticultural species planted in a uniform pattern of rows. The tree crowns do not usually touch, and the understory, composed of grasses and low-growing herbs, is open and may be maintained by mowing or chemical control. Major orchard crops grown in Sutter County include English walnuts, almonds, prunes, and peaches (Sutter County Dept. of Agriculture, 1992). Vineyards are included within this category. Vineyard crops are structured in rows, but usually without spaces within a row. Grasses and herbs are generally allowed to grow between rows to control erosion. Vineyard crops grown in Sutter County include kiwis and various berries.

Orchards and vineyards provide little habitat for wildlife, although they may provide some perching and nesting areas for birds, and evergreen orchards provide some cover for wildlife. Certain wildlife species occasionally become agricultural pests, feeding on nuts and fruits grown in orchards and vineyards, and are therefore often discouraged by various means. Some orchard types, such as almond and olive, provide food for deer, raccoons, rabbits, squirrels, and other wildlife. Almond or walnut orchards adjacent to riparian forests along the Sacramento River are occasionally used as nesting habitat by the state endangered yellow-billed cuckoo (Layman, 1980).

Row or Field Crops

Row or field crops include vegetables, fruits, and grains that are planted in uniform rows. Major crops grown in Sutter County include tomatoes, melons, beans, sugar beets, and various grains (Sutter County Dept. of Agriculture, 1992). Vegetation in this habitat can vary from a few inches to ten feet in height, depending on the specific crop. Densely planted crops form almost complete cover.

Crops such as wheat, barley, and oats are typically planted in the fall and provide some cover for wildlife during the late winter, spring, and early summer. Grain crops are also important food sources for some seed-eating birds, such as pheasant, quail, and dove, and provide grazing to geese and widgeons.

Row and field crops provide good nesting habitat for pheasants, dove, quail, certain waterfowl, and other ground-nesting wildlife species. Harvesting practices, normally begun in June or July, allow these species to complete their cycle of breeding prior to disturbance. These crop types provide substantially higher value to nesting species and their young when they are located adjacent to water, such as drainage ditches or sumps, where cover and foraging habitat is supplied. However, direct destruction of nests and young and indirect destruction through decreased cover and exposure to predators occurs when harvesting is performed in May, the peak nesting month, to increase crop yield (California Waterfowl Association, 1991). Oats, for example, if swathed green for bailing, are harvested in early May during the peak nesting month.

Crops also provide an indirect but limited food source in the form of insects, and cover for birds and mammals but typically do not provide adequate foraging grounds for predators such as raptors. There are some exceptions to this. Corn, for example, provides cover for deer and coyote in the summer, and forage for waterfowl in the winter after harvesting. In the Central Valley, harvested corn fields are one of the primary agricultural lands used by wintering waterfowl (Heitmeyer, 1989), however very little corn is grown in Sutter County.

Irrigated Pasture

Irrigated pasture includes areas of planted perennial grasses and legumes (clover) that compose a uniform and generally complete cover, although the height and density of vegetation varies depending on cultural and grazing practices. When the grasses and clover are mature, livestock is brought in to graze it. Irrigated pasture may be grown in cropland areas as part of a crop rotation program.

Irrigated pasture provides some habitat for grassland-adapted species. Birds using these areas consume seeds, foliage, and insects and may nest on the ground. Small mammals, such as harvest mice and house mice, are attracted to these areas as well. Resident birds of prey, such as red-tailed hawk and black-shouldered kite, a special status species, use these areas for hunting small mammals. Merlin and Swainson's hawk, also special status species, use these types of fields for hunting during the winter migration along the Pacific Flyway. The Aleutian Canada goose, an endangered subspecies of the Canada goose, winters on low, open pasture lands in Sutter County.

IMPORTANT BIOLOGICAL AREAS

Rivers and Bypasses

Sacramento River

The Sacramento River extends for approximately 70 miles along the western border of Sutter County. The river provides aquatic habitat, and the banks support areas of intermittent riparian vegetation between agricultural lands. Resident fish species as well as the winter-run chinook salmon, a federal and state endangered species, occur in the river. Other runs of chinook salmon also use the Sacramento River for spawning, and all are declining in number (Lagomarsino, 1993). Other anadramous fish species that spawn in the Sacramento River include steelhead trout, striped bass, sturgeon, and American shad. Riparian areas along the riverbanks are known to support several special status species, such as migrating willow flycatchers, nesting Swainson's hawk, and valley elderberry longhorn beetle. Bank swallows have constructed colonies of nests in the riverbanks. (CDFG, 1993; Sanders, 1993)

Feather River/Bear River

The Feather River extends approximately 45 miles through Sutter County, forming part of the east Sutter County boundary. The Bear River roughly parallels about 11 miles of the eastern County boundary, crossing the boundary at several points. The confluence of the Feather and Bear Rivers is several miles north of the town of Nicolaus. The Feather River reaches its confluence with the Sacramento River at the southern County boundary near Verona. The section of river between Nicolaus and Verona is bordered by a riparian strip that provides important wildlife habitat, including habitat for special status species such as western yellow-billed cuckoo, Swainson's hawk, and valley elderberry longhorn beetle. This riparian strip has been designated as an Area of Critical Concern by the Sacramento Audubon Society (1989).

Another Audubon Area of Critical Concern includes both sides of the Feather River from Nicolaus north to the Star Bend CDFG Wildlife Area. This 3,700-acre area contains the largest contiguous example of mixed riparian forest remaining in the Central Valley. This area includes Bobelaine Audubon Sanctuary, lands owned and managed by CDFG, and private lands and supports special status species such as the western yellow-billed cuckoo and ringtail as well as a combined great egret, green-backed heron, and great blue heron rookery, many mammal species, and anadromous fish such as salmon (Sacramento Audubon Society, 1989).

Five CDFG management areas make up the CDFG Feather River Management Unit, which includes Abbott Lake (437.8 acres), O'Connor Lake (363.78 acres), Nelson Slough (751.45 acres), Lake of the Woods (662 acres), and Star Bend (50 acres). The former three units, encompassing 1,553 acres, are in Sutter County and the latter two are on the east bank of the Feather River in Yuba County. All five areas are managed by CDFG for fishing, hunting, and other recreational use, and hold water seasonally, except for Abbott Lake which holds water on a year-round basis. Plant communities within these subareas include seasonal wetlands, riparian forest, and, in the Nelson Slough Management Unit, rice fields.

Mammalian wildlife along the Feather River includes black-tailed deer that use riparian woodlands for cover and channel bottoms in the Feather River and Sutter Bypass during periods of low water. Common furbearer species, both terrestrial and aquatic, are also found in this area, including California spotted skunk, striped skunk, raccoon, long-tailed weasel, badger, Virginia opossum, ringtail, beaver, river otter, muskrat, mink, gray fox, and black-tailed jackrabbit. Bobcat and coyote potentially occur in the area, and various small rodents are also present (CDFG, 1991).

A variety of bird species inhabit the riparian areas along the Feather River. A combined great egret and great blue heron rookery exists near O'Connor Lakes, and CDFG has designed management practices to enhance habitat for special status bird species such as Swainson's hawk, yellow-billed cuckoo, bank swallow, and bald eagle (CDFG, 1991). CDFG has recorded the presence of bank swallow, yellow-billed cuckoo, and valley elderberry longhorn beetle along the River (CDFG, 1993).

Aquatic resources of the Feather River include populations of largemouth bass, bluegill, redear sunfish, green sunfish, black crappie, and golden shiner. Channel catfish are found within Abbott Lake (CDFG, 1991).
The Bobelaine Audubon Sanctuary is a 430-acre reserve located within an extensive riparian area along the Feather River near its confluence with the Bear River. The reserve has been primarily used for nature walks and education. A fire in September, 1992 destroyed much of the riparian forest in the Reserve, however, and the area is currently being restored. Sightings of yellow-billed cuckoo and Swainson's hawk have been made within the riparian areas, and bank swallow colonies occur in the river bank (CDFG, 1993; Manolis, 1993).

Sutter Bypass/Tisdale Bypass

The Sutter Bypass, part of the Sacramento Flood Control System, is an artificial flood control corridor approximately 3/4 mile wide, bordered by two parallel channels. The Bypass extends from the Sacramento River in the northwest portion of the County approximately 35 miles south to the Feather River. Within the Bypass corridor are areas of agricultural lands, riparian habitat, and seasonal wetlands. The riparian area along the western levee of the Bypass is an Audubon Area of Critical Concern due to the plentiful wildlife it supports (Sacramento Audubon Society, 1989). The Sutter National Wildlife Refuge, further discussed below, is an extensive area of freshwater marsh habitat located within the Bypass. At the north end of the Bypass is the 178-acre Butte Slough Wildlife Area, which is managed by CDFG. Several sloughs that connect the east and west channels across the Bypass provide smaller areas of stream channel and riparian habitat. Nesting yellow-billed cuckoo have been sighted in riparian areas of the Sutter Bypass in 1992 and 1993, and yellow-breasted chat may also be present (Zezulak, 1993). The Bypass also contains nesting Swainson's hawk, bank swallow colonies, tricolored blackbird colonies, and populations of the rose mallow (California hibiscus). Salmon and warm water fish are also found within the Bypass area (CDFG, 1993).

Another flood control corridor, the Tisdale Bypass, extends for approximately four miles due west from the Sutter Bypass. Its purpose is to channel flood water eastward from the Sacramento River to the Sutter Bypass. The Tisdale Bypass primarily contains upland areas of non-native grassland interspersed with freshwater marsh and riparian areas. Swainson's hawk, a special status bird species, has been recorded here (CDFG, 1993).

Wildlife Refuges

Sacramento National Wildlife Refuges

The Sacramento National Wildlife Refuges (NWRs) include five separate refuges managed by the USFWS (Sacramento NWR, Delevan NWR, Colusa NWR, Butte Sink NWR, and Sutter NWR). The Sutter and Butte Sink NWRs are located in Sutter County. Sutter NWR is a 2,650-acre area within the Sutter Bypass managed by USFWS to attract migratory waterfowl and is used by the public for wildlife observation and hunting, in season. Habitat within the NWR includes freshwater marsh and upland areas of non-native grassland. The Butte Sink NWR includes more than 730 acres of wetlands in the Butte Sink, an important wintering area for waterfowl, and is not open to the public.

Sutter NWR supports a number of raptor species, including northern harrier, black-shouldered kite, and Cooper's hawk, and a small population of black-tailed deer (Sacramento Valley National Wildlife Refuges, 1992). The CDFG has recorded a population of rose mallow (California hibiscus) within the Sutter NWR and wintering Aleutian Canada goose in the Butte Sink NWR (CDFG, 1993).

Waterfowl are plentiful in all of the Sacramento NWRs during winter and early spring. Migration occurs along the Pacific Flyway, a bird "highway" that connects wetlands in the western states. The Central Valley is the most heavily used portion of the Pacific Flyway, supporting about 60 percent of the migrating waterfowl (USFWS, 1993).

Each year, CDFG and USFWS collect and compile data to develop mid-winter indices for wintering waterfowl use in the Sacramento Valley. These indices are counts of waterfowl taken during a short period in January of each year. Although the indices do not represent the maximum number of waterfowl present during a given year, because the Sacramento Valley receives greater use later in the season, they are useful for determining the relative use of different portions of the Valley and for monitoring trends. Two areas of Sutter County are monitored, Sutter NWR and Butte Sink. An examination of the data for these two areas indicates that, for their relatively small size, they host a substantial proportion of the waterfowl wintering in Sacramento Valley. Table 9.8-1 below compiles five-year averages of the mid-winter index data from the Sutter NWR, Butte Sink, and, for comparison, the entire Sacramento Valley (Yparraguirre, 1993). Also, the numbers show a steady and rapid decline throughout the Valley in numbers of birds since 1979.

TABLE 9.8-1
NUMBERS OF WATERFOWL PRESENT IN MID-WINTER

Avg. 1979-1983
Avg. 1984-1988
Avg. 1989-1993

Sutter NWR
312,635
229,095
151,340

Butte Sink
463,373
294,423
282,618

Entire Sacramento Valley
3,107,812
2,425,431
1,903,518

Source: CDFG, 1979-1993
Gray Lodge Wildlife Area

Although only a small part of the 8,400-acre Gray Lodge Wildlife Area extends from Butte County into Sutter County, this region as a whole is important for wintering waterfowl, which may move between the nearby Butte Sink and Gray Lodge. Gray Lodge is managed by CDFG primarily for waterfowl, although upland areas also exist, and is open to the public for hunting, fishing, and sightseeing by car and on foot. A large number of special status bird species have been observed at Gray Lodge including American white pelican, double-crested cormorant, least bittern, osprey, northern harrier, sharp-shinned hawk, Cooper's hawk, golden eagle, merlin, prairie falcon, California gull, burrowing owl, long-eared owl, short-eared owl, willow flycatcher, purple martin, bank swallow, yellow warbler, and yellow-breasted chat. Several additional special status bird species have been observed, but were considered to be of accidental occurrence and are not regular visitors to the area. (CDFG, undated pamphlet)

Privately Owned Waterfowl Concentration Areas

Rice fields and duck clubs in Sutter County are important habitats outside of the NWRs for migrating waterfowl. Although mid-winter counts discussed above are not conducted on private agricultural lands, other data have been collected throughout the County by Michael Miller of the U.S. National Biological Survey in a study of radio-tagged pintail ducks. The portion of these data for southern Sutter County provides an index for waterfowl use on private agricultural lands, primarily rice and irrigated pasture. As in the rest of the County, these areas are most heavily used later in winter (January-March). Table 9.8-2 below shows the percentage of radio-tagged pintail ducks in Sutter County that congregated in the southern part of the County (Miller, 1993). Although these data do not provide total counts of waterfowl using the southern County, it is apparent that this area is a significant part of the Sutter County waterfowl wintering grounds.

Butte Sink

Part of the 80-mile long Butte Basin, the Butte Sink is one of the largest riparian wetland remaining in California (CVHJV, undated). Butte Creek forms the northwest County boundary and borders the Sink where it extends into Sutter County. The Sutter Buttes are adjacent to the southeast portion of the Sink. Outside of the Butte Sink NWR, most of the Sink is privately owned and managed for hunting clubs. The Sacramento National Wildlife Refuge has actively sought conservation easements to preserve wetlands around Butte Sink. As of April, 1995, a total of 6,731 acres of wetlands were protected by such easements. Butte Sink is a key wintering area for waterfowl that use the Pacific Flyway, which is a primary migration route for waterfowl in North America (Dan Yparraguirre, 1993). The CDFG records yellow-billed cuckoo nesting within Butte Sink, Aleutian Canada goose wintering in flooded fields at the south end of the Sink, as well as populations of rose mallow (California hibiscus) (CDFG, 1993). The Sink also contains areas of alkaline wetlands that provide potential habitat for special status plants (Ahart, 1993).