Chapters 1 - U.S. Fish and Wildlife Service

Chapter 4
A variety of foraging habitats are available for the different guilds of birds observed on the Refuge.
Shorebirds feed mostly on invertebrates present within the mudflats and tidal channels, while
gulls, terns, cormorants, grebes, egrets, herons, and pelicans forage on a variety of fish species
present within the subtidal and intertidal zones of the marsh. Dabbling ducks eat plant material,
including eelgrass, and/or invertebrates in shallower waters and diving ducks prey on
invertebrates or small fish in deeper waters. Canada geese (Branta canadensis), which tend to
feed on grasses, seeds, and sprouts in adjacent upland areas, use the marsh as a resting area.
Wintering Birds
The Refuge’s bird populations can be divided into several broad categories according to when they
are present. The greatest species diversity and overall bird abundance on the Refuge occurs when
wintering birds (consisting primarily of shorebirds, waterfowl, and raptors) are present. The
Refuge’s tidal and intertidal habitats are important foraging and resting areas for these and other
birds traveling along the Pacific Flyway. Shorebirds, generally the first to arrive, can be expected
in August, with the first ducks generally following in September. Past observations indicated that
peak bird abundance is typically observed from November through February. Those birds that
choose to stay on the Refuge for the entire winter are generally present until April.
Raptors, which are also included in this group of wintering birds, are most abundant on the Refuge
in the fall and winter. Of the fifteen species of raptors that have been documented on the Refuge
and surrounding NWSSB lands, six species are present to some extent throughout the year. These
species include osprey, northern harrier, Cooper’s hawk, red-tailed hawk, American kestrel, and
peregrine falcon. Other less common species, such as ferruginous hawk, merlin, and prairie falcon,
are seasonal visitors generally observed during the fall and winter months. Some of these species
stop for a while to hunt and refuel, while others may spend the entire winter in the area. The
marsh provides significant foraging habitat for a variety of raptors including osprey, northern
harrier, peregrine falcon, red-tailed hawk, merlin, and kestrel. Other species forage in the open
grasslands on NWSSB and may be seen roosting on a power pole or other structure within the
Refuge.
Another wintering bird of interest on the Refuge is the Nelson’s sharp-tailed sparrow
(Ammodramus nelsoni). This species, which forages on insects, spiders, snails, and seeds,
typically winters along the Atlantic Coast from New York to Florida and along the Gulf Coast from
Florida to Texas (Cornell Lab of Ornithology 2003). However, the species can also be found
wintering in a few areas along the California coast (Sibley 1996), including Seal Beach NWR.
When present, this species can be found within the shrubby habitat along the northern and eastern
edges of Hog Island.
Migrant Birds
Another category of birds supported by the Refuge are migrant birds that use the wetlands as
feeding and resting stops on their journeys between breeding and wintering grounds. Migratory
birds moving south for the winter generally begin arriving at the Refuge in late summer, and are
most abundant in the fall. Spring migration generally occurs from February through May for
species heading north. Some of the Refuge’s spring migrants include Wilson’s phalarope, rednecked
phalarope, black tern, white-throated swift, green heron, and common merganser (CDFG
& USFWS 1976).
Summer Residents
Summer residents, the third category of the birds that utilize the Refuge, are present in much
smaller numbers than are wintering birds. Many of the summer residents arrive at the Refuge
4-48 Seal Beach National Wildlife Refuge