School and Group Programs
Mandala of the Seasons: Winter
Winter Weather
Winter storms bring wind and rain to the Headlands. Most of the rain that falls in the headlands in any given year falls between December and March. In the Winter of 2000, it rained 22 out of 29 days in February.
If you are visiting the Headlands Institute in the winter, be sure to bring rain pants and a rain jacket, or a heavy duty poncho.
Winter Animals
California Newt
Photo Credit: Jens V. Vindum, California Academy of Sciences
The abundance of rain in the winter creates lots of pools, puddles, and muddy trails throughout the Marin Headlands. These soggy conditions are favorable for amphibians, such as newts, frogs, and toads. During this time, adult California newts migrate from their dry season habitat underneath rocks and logs to temporary pools for mating.
Like frogs, newly hatched newts will go through a tadpole development stage in the water. When they mature, the young newts will be able to survive on land. Here in the Headlands, some California newts use the ditch beside the Rodeo Valley trailhead and the old gun-emplacement in Battery Townsley as breeding pools. Newts have bright orange bellies that warn potential predators that they are poisonous.
When winter hiking in the Marin Headlands, keep your eyes open for these amazing animals in the temporary pools besides the trails. You'll be surprised by the amazing life that flourishes in these basins of rainwater!
Winter Plants
Some of our native shrubs, including poison oak, have no leaves during the winter. Other plants, like the annual grasses, thrive during the wet season. Annual grasses are the primary cause of the greening of the otherwise brown, or golden, hills of the Bay Area.
Wild Cucumber in bloom Photo credit: Dr. Alfred Broussea of Saint Mary's College
Wild cucumber Marah fabaceus, is a n
ative vine that has a noticeable growth spurt each winter and then dies back later in the year. As it grows, the tendrils of the cucumber wrap around the branches of other plants, using them for support. This is called thigmotropism. Wild cucumber, also known as California Manroot, is endemic to California, meaning it grows no place else.
Winter Water
The majority of rainfall in the Marin Headlands comes during the winter. In the
Rodeo Valley watershed, rain that falls on the hills seeps down into the valleys, flows into Rodeo Creek, and finally collects in Rodeo Lagoon. Rodeo Beach prevents the water in the lagoon from reaching the ocean. As the rains continue, the water level gradually rises and the lagoon swells. So much water is stored at this point that the lagoon threatens to flood the footbridge that crosses to the beach.
With nowhere else to go, the water eventually spills over the beach and carves a channel to the ocean. As if in a sigh of relief, the trapped lagoon water rushes out through the channel to join with the ocean water. This channel drains the lagoon and the water level of the lagoon drops dramatically. At high tide this flow may be reversed, as the channel allows rising sea water to flow into the lagoon.
Saltwater makes its way into the lagoon in another way too. Wind from winter storms at sea can create huge waves. A few days out of the year, the waves are big enough (25 feet, for example) to crash over the beach and trickle down into the lagoon. This event adds saltwater to the lagoon and gives it its characteristic brackish quality, a mix of fresh and salt water. The formation of the channel and the flow of saltwater into the lagoon only happen in the winter when heavy rains fill up the lagoon and storm surges erode the beach.
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