Burrough Valley - Natural History

Natural History

Burrough Valley’s primary geological feature is granite but with considerable sedimentary and metamorphic formations. The climate is relatively dry with an average annual rainfall of about 20-25 inches but varying greatly within a range of less than 10 inches (250 mm) to more than 40 inches (1,000 mm). The area is grassland or savannah and chaparral. The valley's trees include the valley oak, the blue oak, and the interior live oak. Along the intermittent streams are found willows, cottonwoods, and white-barked sycamores. South facing hillsides are relatively barren, with scattered patches of buck brush (ceanothus) and scrubby blue oaks and live oaks. North facing hillsides are often covered with thick manzanita, poison oak, live oak, California buckeye (aesculus californica) and buck brush. In the spring, especially after wet winters, wildflowers proliferate, including the California poppy, the Mariposa lily, many forms of lupin and brodiaea.

Burrough Valley is habitat to many animals and birds, including black-tailed deer, mountain lion, bob cat, coyote, cottontail, gray squirrel, California ground squirrel, and many smaller rodents. Wild pigs were introduced or migrated to the area in the 1980s. Feral pigs, which escaped from early settlers, were once common in the 1900s and early 20th century. Reptiles inhabiting the area include the northern Pacific rattlesnake, gopher snake, two species of king snake, garter snake, northern alligator lizard, western fence lizard, skink, and whiptail lizard. The area’s amphibians include the tree frog, California newt, several species of salamander, toad, and American bull frog, which was introduced in the 19th century. The leopard frog once was common, but is now rare. Golden eagles occasionally soar high above the valley and make their nests in the remote rocky crags on the mountain tops. Red-tailed hawks often ride afternoon thermals. There are also Cooper’s hawks and sharp-shinned hawks and two species of kestrels. Turkey vultures spend most of the year in the area but migrate south in winter. Crows are common. Other birds include meadow larks, mourning doves, starlings, scrub jays, Steller’s jays, blackbirds, sparrows, towhees, western bluebirds, Wilson’s warblers, western flycatchers, titmice, humming birds, and many other small birds. Wild turkeys, introduced in the 1960s, are common. Band-tailed pigeons enter the valley in the fall and winter to feast on acorns. The commonest bird is perhaps the acorn woodpecker, whose raucous laugh can be heard nearly every daytime moment. Several other species of woodpeckers are found, including the red-shafted flicker, Lewis's Woodpecker and downy woodpecker. California Valley Quail are also common, with their call “chi-ca-GO! chi-chi-ca-GO!” heard frequently.