Tour stop: Salt Pond Observation Deck

Bird Migration

Many birds are migratory, meaning they travel long distances between the places they breed and the places they spend the winter. As the weather gets warmer in the spring, migratory birds typically travel north to take advantage of burgeoning food resources, especially insects. As the weather gets cooler in the fall, migratory birds travel to warmer areas where more food is available in the winter months.

The Don Edwards National Wildlife Refuge lies within the Pacific Flyway, a major migratory route for birds. Along this migratory route, some birds may travel thousands of miles to places as far away as Alaska or South America. Such a long journey requires a lot of energy! Because the refuge provides abundant food for birds, many species stop here during spring and fall migration to rest and feed before continuing on their epic journeys.

Some migratory birds that spend the winter here include several duck species, such as the Bufflehead, Canvasback, and Red-breasted Merganser, as well as grebes, including the Eared, Western, and Clark’s Grebe. Take a close look at nearby vegetation or on the ground and you may see and hear smaller migratory birds, such as White-crowned Sparrows, Golden-crowned Sparrows, and Yellow-rumped Warblers.

If you’re visiting in the summer, other migratory birds you may find include Barn Swallows and Cliff Swallows zooming through the sky catching insects. If you’re lucky, you may also see shorebirds spinning in circles in the water. These birds are called phalaropes, and their peculiar spinning behavior forces water away from the surface, causing an upward flow of water from below with a bounty of food!

3-A-Bird Migration

Year-round Birds

The Don Edwards National Wildlife Refuge is a hotspot for birds year-round, providing ideal habitat and plenty of food. Gazing over the salt ponds and mudflats, you may see shorebirds such as American Avocets and Black-necked Stilts roosting or feeding. Mallards, Gadwalls, Canada Geese, and American Coots are common sights floating on the water or resting near the water’s edge. Large wading birds, including the Great Blue Heron, Great Egret, and Snowy Egret can also be found here throughout the year using their spear-like bills to catch fish and other prey. Scanning the marsh, you may even catch a glimpse of a hawk, such as the Red-tailed Hawk and Northern Harrier. Among the vegetation, listen for the buzzy trills of songbirds that call the refuge home all year long, including the Savannah Sparrow, Marsh Wren, and Red-winged Blackbird. Look up at the sky and you may notice Turkey Vultures soaring overhead or California Gulls flocking and calling. No matter where or when you visit the refuge, you’re bound to see some wildlife nearby!


Breeding Birds & Decoys!

Because the Don Edwards National Wildlife Refuge provides great habitat for birds, many species breed here every year. You may find Pied-billed Grebes sitting on nests in shallow water, or Black-necked Stilts and American Avocets nesting on the ground near the water. Many other species also breed in the refuge, from tiny Anna’s Hummingbirds and Savannah Sparrows to awe-inspiring White-tailed Kites and Peregrine Falcons.
As you scan the ponds, you may notice islands with what appear to be birds sitting very still on them. These human-made islands were constructed in former salt ponds to help attract birds and provide nesting habitat for them. The statuesque birds you see may in fact be decoys! These tern decoys and a colony call playback system were placed on the islands to help attract Forster’s Terns (Sterna forsteri), a species that was once one of the most numerous colonial-breeding waterbirds in South San Francisco Bay, but whose numbers have declined in recent years. In 2019, with the help of the decoys and nesting islands, Forster’s Terns re-established a breeding colony in the pond for the first time in 8 years!

Breeding Birds

Food Chain

If you take a closer look at the marsh water, you’ll find countless small critters called zooplankton that swim around and eat microscopic plants called phytoplankton. These small plants and critters, some that cannot be seen with the naked eye, are the foundation of the food chain of the non-tidal slough habitat. A food chain is a sequence that shows the organisms that feed on each other. For example, phytoplankton is eaten by zooplankton, zooplankton is eaten by small fish, small fish are eaten by larger fish, and larger fish are eaten by birds. Within the non-tidal slough ecosystem that are many food chains. Pollutants such as pesticides that enter the Refuge through urban runoff threaten the health and balance of the non-tidal slough food chain.

3-D-Food Chain

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