Habitat and Wildlife at Sacramento NWR Complex



The Sacramento NWR Complex provides essential habitat for a great diversity of wildlife, particularly migratory birds of the Pacific Flyway. Approximately 95% of the historic wetlands, riparian riparian
Definition of riparian habitat or riparian areas.

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areas, and grasslands in the Central Valley have been destroyed or modified. The Complex maintains nearly 70,000 acres of wetland, upland and riparian habitats.

Seasonal Wetlands

Seasonal wetlands make up the majority of the refuges' wetland habitat.  They are flooded from fall through spring, and then are dry from late spring through summer.  When ponds are drawn down in the spring, seed-producing plants germinate and grow on the moist pond bottoms. The seeds and invertebrates these ponds produce become available to waterfowl and other wetland species when they are flooded in the fall. Seasonal wetlands provide important resting and feeding habitat for waterfowl, shorebirds, egrets, herons, raptors and other wetland-dependent wildlife from fall to spring. Common plants include cattail, hardstem bulrush, alkali bulrush, and swamp timothy.


Irrigated Seasonal Wetlands

Some seasonal wetlands (described above) receive an irrigation during the spring or summer months in order to increase seed and vegetative production.  Irrigations can last for a few days or over a month, depending on weather conditions and plant response.  Shorter irrigations can enhance smaller stature plants, like swamp timothy, while longer irrigations can bring taller plants, such as watergrass and smartweed, to full maturation.  Other plants that also respond with vigorous growth include sprangletop, spikerush, Bermuda grass, and joint grass.  Because of the high seed production, irrigated seasonal wetlands have the highest waterfowl use, but tend to have decreased use by shorebirds due to the taller and denser plant structure structure
Something temporarily or permanently constructed, built, or placed; and constructed of natural or manufactured parts including, but not limited to, a building, shed, cabin, porch, bridge, walkway, stair steps, sign, landing, platform, dock, rack, fence, telecommunication device, antennae, fish cleaning table, satellite dish/mount, or well head.

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Permanent/Semi-Permanent Wetlands

Permanent wetlands are flooded year-round and provide a water source that is valuable to resident wildlife, especially during the summer when most of the seasonal wetlands are dry. Semi-permanent wetlands are flooded from fall through summer, and are dry for a short window in late summer so that plant germination and nutrient recycling can occur.  During the summer, when flooded habitat is scarce, these ponds provide nesting areas for resident waterfowl and other wildlife. During the fall and winter, they add to the important resting and feeding areas on the refuge. Characteristic plants include cattail, hardstemmed bulrush, burhead and sago pondweed.


Riparian Areas

Riparian areas tend to grow in linear areas along the edges of rivers, creeks, and waterways and can characterized by the thick growth of trees and shrubs.  This scarce waterside habitat supports a great diversity of wildlife. It is heavily used by neo-tropical migrant bird species such as the yellow-billed cuckoo, black-headed grosbeak, spotted towhee and dozens of songbird species. It also provides important breeding habitat for colonial nesting egrets and herons, as well and raptors, such as hawks, eagles and owls. Cottonwoods, valley oaks, sycamores, willows, box elders, elderberry, and wild rose are common plants found in riparian areas.



Upland areas include a mixture of grasslands and vernal pool/alkali meadow habitats. Many of the grassland areas have been restored to native grasses and wildflowers. In areas with more alkaline (salty) soils, rainwater tends to naturally puddle in depressions and create what are referred to as "vernal pools".  Salt-tolerant native plants grow well in these alkaline areas.  In the spring, these areas produce a carpet of protein-rich grass shoots and vernal pools are often filled with invertebrates, providing an important food source for waterfowl and shorebirds that are preparing for spring migration.  During the spring and summer months, they provide nesting habitat for ducks, pheasants, meadowlarks, burrowing owls, bitterns, and northern harriers. In the winter and spring, annual grasses provide food for geese, coots, and wigeon. They also support significant numbers of insects, rodents, and reptiles which in turn are important forage items for raptors and birds. Goldfields, downingia, and popcorn flowers bloom brilliantly on the edges of the vernal pools in late spring. Other plants include: saltgrass, saltbush, and annual grasses.



Seasons of Wildlife

Each season brings a new look to the refuges with a variety of wildlife.  There's always something to see, whether its waterfowl in the winter, shorebirds in the spring/fall, or breeding neotropical migrants in the summer.
 Seasons of Wildlife <-- Click here to learn more about what wildlife you might see during the year.

Wildlife Checklist

Along with the millions of waterfowl, shorebirds, raptors, waterbirds and migrant songbirds that can be found using the refuges of the Sacramento NWR Complex, there is also a small variety of mammals including opossums, raccoons, coyotes, skunks, jack rabbits, river otters, beavers, muskrats, and more that live on the refuge.  
Wildlife Checklist  <-- Click here to see the Complex's Wildlife Checklist.

Reported Sightings

What wildlife have visitors and staff been seeing on the Complex? We encourage visitors to report to us any sightings of rare, unusual, or unique animals on our refuges and the surrounding areas. Check out the most recent sightings on eBird.

Waterfowl Surveys

Refuge biologists conduct monthly waterfowl surveys. 
Waterfowl Surveys  <-- Click here to see the Complex's Waterfowl Surveys 

How are surveys conducted?
Wildlife surveys are conducted once a month, mid-month, on all wetland refuges of the Sacramento NWR Complex.  All waterfowl, shorebirds, waterbirds, gamebirds, raptors, and a handful of mammals and other songbirds are tallied on every single unit (pond/field), using a standardized survey route, a window-mounted spotting scope and binoculars. Using the same observer for each refuge helps maintain consistency (some of the biologists have maintained their routes for over 20 years), assuring a strong index over time.

Routes are designed to take advantage of vegetation barriers, viewing lanes, and flight patterns to maximize viewing, reduce disturbance, and increase the likelihood that flushed birds will fly to an area that the observer has already counted. The observer approaches each pond and takes an initial count. When numbers per pond are low (in the hundreds), a count of each species is done separately. When numbers per pond are in the thousands, all species except for ducks are counted separately, and then ducks are counted as one group and a species composition is applied to that group (ie 1% mallard, 4% gadwall, 10% shoveler, 20% wigeon, 25% green-wing, 40% pintail).  Composition can change even within a pond, as some species such as teal will concentrate in certain areas, so multiple groups may be counted and described with different compositions across a single pond.

Depending on flock size, birds may be counted as singles, or in groups of 5, 10, 20, 50, 100, or even 1000 (the only option when a group of 20,000 birds take flight). The smaller the grouping that the observer uses for counting, the higher the accuracy.

Each pond/field is scanned from multiple viewing points, with the goal of seeing and counting all visible wildlife.  Auditory cues can also be used, especially for secretive marsh birds such as rails or bitterns.

Following a survey week, biologists transcribe their data and enter it into a database. This data is then used to analyze bird use of each pond/field, and can be tied to management data to assess the effectiveness of past treatments, or identify the need for future efforts. It helps managers identify units that are critical for supporting wintering waterfowl, breeding birds, or special status species, which in turn guides decisions when facing drought, water restrictions, invasive species invasive species
An invasive species is any plant or animal that has spread or been introduced into a new area where they are, or could, cause harm to the environment, economy, or human, animal, or plant health. Their unwelcome presence can destroy ecosystems and cost millions of dollars.

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or other threats. When rolled up to the refuge level, population trends and distributions over time can be assessed. The data is also pulled to feed into larger survey efforts for a variety of species groups at a statewide level.

Wildlife Depredation Issues?

If you are experiencing problems with wildlife depredation on your private property, you can find information about what you can do by visiting USFWS Migratory Bird website.

Mountain Lions

Mountain lions are residents along the Sacramento River, and there are occasionally sightings on Sacramento River NWR, and rarely on the other refuges of Sacramento NWR Complex.  Click here to learn more.

Endangered and Threatened Species

The Sacramento National Wildlife Refuge Complex is home to a number of Federal and State threatened and endangered species. Click here to see a List of Threatened and Endangered Species that occur here.