Terms and concepts related to hiking, birding, and the natural environment found in the Silicon Valley area.
Hiking
Elevation gain
Elevation gain is a measurement of how much you climb (in feet or meters) from the start to the highest point of a hike. Keeping track of elevation gain helps you understand the difficulty and intensity of a trail.
Fire road
A fire road is a wide, unpaved road primarily intended for emergency vehicles, especially for wildfire response. Many of Silicon Valley’s open space preserves use these roads as multi-use trails.
Flow trail
A flow trail is a type of mountain biking trail designed with smooth contours, berms, and gentle grade changes that give riders a “flowing” sensation as they cycle from one end to the other.
Gargoyles
In trail design, “gargoyles” are large rocks placed strategically to guide foot traffic, divert water, or deter off-trail shortcuts. The term borrows from architectural gargoyles, which channel rain away from buildings.
Interpretive signage
Interpretive signage provides educational information along trails, highlighting local wildlife, geology, or cultural history. Look for these signs at trailheads or key points of interest in open space preserves and other park systems to learn more about the area’s natural and cultural features.
Leave no trace
Leave No Trace is a set of guidelines promoting responsible outdoor recreation. It includes packing out all trash, minimizing the impact of campfires, not removing any plant or animal materials from open space preserves, respecting wildlife, and staying on designated trails, when required, to protect fragile habitats.
Social trails
Social trails are unofficial pathways created by repeated foot traffic rather than formal design. They often develop when people take shortcuts off a main trail, walk around obstacles, or explore a particular scenic feature.
Switchback
A switchback is a sharp trail turn—often a zigzag pattern—used to moderate steep inclines or declines. Switchbacks help hikers gain or lose elevation gradually and prevent severe erosion on hillsides.
Trailhead
A trailhead is the starting point or entrance to a hiking trail. Trailheads often have maps, informational signs, and sometimes parking or restroom facilities.
Birding
Passerine
Passerines—also called perching or songbirds—are birds characterized by three toes facing forward and one backward, which helps them grip branches. Common passerines in Silicon Valley include finches, sparrows, and warblers.
Raptor
Raptors are birds of prey such as hawks, eagles, and falcons. In Silicon Valley, species like the red-tailed hawk, red-shouldered hawk and Cooper’s hawk are frequently spotted soaring above open fields or perched in tall trees scouting for prey.
Open Space and the Environment
Baylands
Baylands are wetlands and salt marshes adjacent to the shores of the San Francisco Bay. These areas often include tidal mudflats and pickleweed (a salt-tolerant plant). Many migratory shorebirds and waterfowl rely on baylands as stopover sites to rest and feed during long journeys.
Boardwalk
A boardwalk is a raised walkway, usually made of wooden planks or composite materials, that helps people walk in wet or sensitive areas without trampling vegetation. Boardwalks are common in marshy sections of Silicon Valley trails, protecting wetlands while providing a dry footpath.
Chaparral
Chaparral is a habitat dominated by dense, evergreen shrubs such as manzanita and chamise. This plant community is found in Mediterranean climates with hot, dry summers and mild, wet winters. Plants in chaparral landscapes have adaptations like thick, waxy leaves to conserve water.
Duff
Duff is the layer of decomposing leaves, needles, and other organic matter that accumulates on the forest or woodland floor. This layer helps maintain soil moisture, provides nutrients for plant growth, and can offer cover for insects and small animals.
Ecotones
Ecotones are transition zones between two distinct ecological communities—such as the border between a riparian woodland and a grassland. Because they often contain species from both adjoining habitats, ecotones tend to have high biodiversity and serve as vital wildlife corridors.
Endemic
An endemic species is one that occurs naturally in only one geographic region.
Habitat fragmentation
Habitat fragmentation occurs when continuous habitats are broken into smaller, isolated patches—often due to roads, development, or agriculture. This makes it harder for wildlife to move freely, find resources, and maintain healthy breeding populations.
Invasive species
Invasive species are non-native plants or animals introduced—often by human activity—that spread quickly and outcompete local species for resources.
Lichen
Lichen is a symbiotic partnership between a fungus and an alga (or sometimes a cyanobacterium). You often see lichens on rocks, tree bark, hanging from tree branches, and fence posts in Silicon Valley’s woodlands and grasslands. They serve as good indicators of air quality because many lichens are sensitive to pollution.
Native species
A native species is one that naturally evolved in and inhabits a specific region.
Nesting season
Nesting season is the period during which birds build nests, lay eggs, and raise their young. In Silicon Valley, many species begin nesting as early as February and continue through late spring or summer.
Nodding flowers
Nodding flowers are wildflowers with petals that hang downward from their stems, creating a drooping or pendulous appearance. This downward orientation can help protect pollen from rain or direct sun, while still granting access to pollinators like hummingbirds and bees.
Oak woodland
Oak woodlands is a plant community containing oaks with open grasslands or shrub understories beneath them. Oaks produce acorns, an important food source for many local birds and mammals, making these habitats essential for biodiversity.
Riparian zone
A riparian zone is the interface between land and a flowing body of water (like a river or creek). These areas in Silicon Valley often feature willows, sycamores, and cottonwoods.
Understory
The understory is the layer of vegetation growing beneath a forest canopy but above the ground layer. In local conifer or oak woodlands, the understory can include shrubs like toyon and coffeeberry, as well as young saplings and wildflowers.
