Savanna-like oak woodlands are among the most characteristic of Bay Area plant communities, and the only wooded areas of San Francisco prior to human habitation. Dominated by oak trees, these complex and diverse habitats harbor more wildlife than any other terrestrial plant community in the Bay Area. Coastal live oaks grow in sheltered ravine areas, and a remnant area of this ecosystem was left intact when Golden Gate Park was created.
Oaks can be either deciduous or evergreen. The oak species found in San Francisco is the evergreen Coast Live Oak. The oak tree provides sustenance for many birds and mammals. Gray squirrels and scrub jays are voracious consumers of acorns from oak trees. Scrub jays may bury several thousand acorns in one season. By hiding and sometimes forgetting about their food stashes, Scrub Jays are planting future trees.
Oaks provide habitat for a variety of birds and insects. Coast live oaks host more species of small moths, for example, than any other plant species on the San Francisco peninsula. Small forest birds, such as the Chestnut-Backed Chickadee and the Hutton’s Vireo, depend on oaks for nesting and feeding habitat. Sapsuckers drill into the bark for food, Western harvest mice consume bark and Botta’s pocket gophers eat the roots of saplings. Insectivorous birds such as Brown Creepers and Nuthatches feed on insects residing on the trunks, branches and leaves of oaks. Oak trees are especially valuable to the many species of migratory birds that are in San Francisco for only part of the year.
Insects and mammals find new leaves on oak trees particularly tasty. The oak tree combats this predation by producing tannins and other chemicals distasteful to herbivores. As a result, animals are discouraged from eating too many leaves, allowing saplings to survive.
Oak acorns were a staple food source for the Ohlone in San Francisco. Oaks provided the wood for bowls, utensils, and fires. The Ohlone also used tannins from oaks for dye and tattooing. Tannins were also used to treat a variety of ailments from fevers to gastrointestinal problems. Oak bark was used for tanning hides by European settlers and oak charcoal was used to make mortar, plaster and fertilizer.
The oak woodland community may also include toyons, pink flowering currant, oso berry, coffee berry and many other species.
Oak woodlands can be found on Yerba Buena Island, in Buena Vista Park, and in Golden Gate Park at Coon Hollow, Casino Hill, Chicken Hill, Strawberry Hill, Whiskey Hill, and McLaren Ridge.
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