San Marcos Foothills Bird Ecology

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San Marcos Foothills Bird Ecology

At least 126 species of birds have been documented on the San Marcos Foothills. Forty of these are known to breed in the Foothills. The SMF Grasslands are occupied extensively by birds year-round, but some breeding species are replaced by migrants that spend the fall and winter. A third group of birds, those that only pass through on migration, can be especially abundant in spring.

BIRD ECOLOGICAL GUILDS:

Two species-rich groups of birds are present on San Marcos Foothills, seedeaters and birds of prey. They occupy two distinct niches, that is, each serves a particular ecological role exploited by each member in a different way. Such groups are known as guilds. The two guilds are linked ecologically by their use of grasslands, although their activities take in other habitats as well.

Grassland Seedeaters

Members of the seedeaters guild feed mostly on seeds in the fall and winter and mostly on insects during the breeding season in spring and summer. (See Table below.) In fall and winter, flocks of Western Meadowlarks (sometimes exceeding 100 individuals), Red-winged Blackbirds, Mourning Doves, and European Starlings feed on insects and seeds among all the grasslands. Savannah Sparrows, as well as smaller numbers of Lark Sparrows, Lincoln’s Sparrows, Vesper Sparrows, and Grasshopper Sparrows are present. In spring and summer, Grasshopper Sparrows are the star attraction, but Rufous-crowned Sparrows, Lazuli Buntings, and Lark Sparrows are well-represented also.

The San Marcos Foothills is the first confirmed breeding locality for Grasshopper Sparrows along the South Coast of Santa Barbara County. In the North County, Grasshopper Sparrows breed in scattered locations from the coast to the foothills of Figueroa Mountain. In the early 2000s, Grasshopper Sparrow population were very dense at that on San Marcos Foothills—at least one pair for every five to six acres of grassland.

Seed eating Assemblage on San Marcos Foothills

Breeding Season (March to July)

Non-breeding Season

Black-headed Grosbeak

Spotted Towhee

Lazuli Bunting

California Towhee

Spotted Towhee

Rufous-crowned Sparrow

California Towhee

Vesper Sparrow

Rufous-crowned Sparrow

Savannah Sparrow

Lark Sparrow

Grasshopper Sparrow

Song Sparrow

Fox Sparrow

Mourning Dove

Song Sparrow

Lincoln's Sparrow

Chipping Sparrow (migrant)

Golden-crowned Sparrow

White-crowned Sparrow

Dark-eyed Junco

Western Meadowlark

Mourning Dove

Red-winged Blackbird

Twenty-one seedeating bird species can be found throughout the year on San Marcos Foothills. The grasslands provide the seeds and the insects for most of these guild members.

Birds of Prey and Their Prey

Nocturnal and diurnal predators are ever-present in the grasslands. Coyotes are present daily and the more reclusive Bobcats and Gray Fox are thought to forage each night. Also present year-round are Red-tailed Hawk, Red-shouldered Hawk, Cooper’s Hawk, Greater Roadrunner, Turkey Vulture, White-tailed Kite, American Kestrel, Barn Owl, and Great Horned Owl. Additional predators in winter include Burrowing Owl, Northern Harrier, Sharp-shinned Hawk, Merlin, and Zone-tailed Hawk.

Because the prey preferences of these predators is rather well established, we can surmise that certain prey are in ample supply on San Marcos Foothills. Burrowing Owl feed primarily on Jerusalem Crickets. California Voles are the preferred prey of White-tailed Kite, pairs of which use the West Mesa and the Cieneguitas Creek Grasslands. Other small mammal fauna, so important in support of the birds of prey assemblage, are poorly known on San Marcos Foothills. Brush Rabbits may be the principal prey for Red-tailed Hawk. Other small mammals (Deer Mouse, California Mouse, pocket mice, shrews, and snakes) must be present in ample abundance but the lack of any formal investigations on small mammals does not allow us to detail the prey base for the predators on San Marcos Foothills. Mourning Dove and Western Meadowlark are heavily preyed upon, probably by Coyote and Red-tailed Hawk. Greater Roadrunner eats almost anything up to one-third its body size: lizards, snakes, nesting and nestling birds, small mammals, and large insects. There are few places other than San Marcos Foothills in Santa Barbara County where one can reliably see a Greater Roadrunner.

Droughts in our regions are profoundly stressful events for birds. Because the bird breeding season is compressed for most species between late April and early July (beyond most of the rainy season), habitats that retain moisture are those that support most bird reproduction. This explains why riparian habitats support a very high proportion of nesting birds in southern California. Each wetland habitat is important in proportion to its size, persistence, water chemistry, and association with other habitats. Insects, soil micro-organisms, amphibians, and plant communities are the primary beneficiaries of wetlands; reptiles, small mammals, and birds are in turn supported. Surface wetlands are therefore important contributors to ecosystem functions in the semi-arid Santa Barbara region

Birds of Prey Assemblage on San Marcos Foothills

Breeding Season (February to August)

Non-breeding Season

Turkey Vulture

White-tailed Kite

Northern Harrier

Cooper's Hawk

Sharp-shinned Hawk

Red-tailed Hawk

Red-shouldered Hawk

Red-shouldered Haw

American Kestrel

Zoned-tailed Hawk

Barn Owl

American Kestrel

Great Horned Owl

Merlin

Western Screech-Owl

Burrowing Owl

Western Screech-Owl

Loggerhead Shrike

More than any other group, small mammals (voles, gophers, various mouse species, White-footed Woodrat, Merriam’s Chipmunk, and California Ground Squirrel) support the SMF bird-of-prey community. Protecting birds of prey requires an understanding of these smaller animals — the habitats they use and the passage corridors to other habitats they depend upon – so that stewardship practices may be compatible with their needs.

Other Bird Groups

Flycatching insectivores are well-represented at San Marcos Foothills, but, as in the other guilds, the species constituents differ by season. In winter, Black Phoebe, Say’s Phoebe, Cassin’s Kingbird, and American Kestrel are the principal aerial insectivores. During spring migration, large numbers of Barn Swallows, Northern Rough-winged Swallows, Cliff Swallows, and Western Kingbirds make prolonged visits to the Grasslands, fueling up here en route to breeding grounds. In summer, Acorn Woodpeckers, American Kestrel, Cassin’s Kingbird, Black Phoebe, and Ash-throated Flycatcher occupy this niche. Bats are another aerial insectivore group that have been observed but not yet inventoried on the Foothills.