Natural Bridges State Beach
Natural Bridges State Beach is a 65-acre park in California located between the Pacific Ocean and the city of Santa Cruz just to the north of Monterey Bay.
The park is known for its tide pools, opportunities to view wildlife such as shorebirds, migrating whales and otters, and monarch butterfly visitors.
The park has two wildlife preserves as well as the beach. Moore Creek flows through the park on one side creating both fresh water wetlands and salt marshes before crossing the beach to the ocean. This area is designated as the Moore Creek Wetlands Natural Preserve while the other side of the park is designated as the Monarch Butterfly Natural Preserve.
Monarch Butterflies are warm weather lovers who, during the spring and summer, live in areas west of the Rocky Mountains where milkweed, their necessary companion plant, is found. This photo (courtesy of Wikimedia Commons) shows a male Monarch drinking nectar from the milkweed flower. Females lay their eggs on milkweed leaves which then serve as the food source for Monarch caterpillars. Milkweed contains a toxic compound that makes the caterpillars toxic to potential predators thus protecting them.
The Monarch is the only butterfly known to make migrations similar to those of birds. However, unlike birds, the butterflies that leave their winter home are not the ones who return the next year. The butterflies leave where they over-winter, and, after traveling a few hundred miles, stop to lay eggs. These adult butterflies die, and the next generation continues the journey. It might take four or more generations to actually reach their summer home. Each generation only lives a few weeks. At the end of the summer, a generation is born that will live up to 9 months, a “super” generation. This generation rides air currents to where they will over-winter starting the cycle again. It is unknown why this generation is so long-lived.
Natural Bridges State Park’s Monarch Grove often provides a home for thousands of these butterflies. The grove contains eucalyptus trees in a gently sloping canyon. The canyon protects the butterflies from coastal winds while the winter-flowering eucalyptus trees provide a source of food. When the weather is warm, the butterflies take to wing feeding on the eucalyptus and milkweed flowers in the canyon.
When the temperature dips below 60 degrees, these heat-loving butterflies cluster together into “cities” of butterflies for warmth high up in the tall trees as seen in this photo. The clusters are formed as they inter-twine their legs to protect individuals from being displaced by any wind.
The Monarchs begin to arrive in late October and leave in February or March. The best viewing time is typically in November and December when the greatest concentrations are usually in residence. You can hike the Monarch Trail into the canyon to search for them. The trail begins as wheelchair accessible boardwalk with interpretive signs of Monarch facts. The boardwalk leads to two observation platforms. Wheelchair accessibility ends at the second platform. Beyond this point, the trail continues as a foot trail with a section that requires climbing over some roots that heads north and connects to the Moore Creek Trail completing a loop to the beach. The total distance is a little less than a mile. I didn’t see butterflies at any of the observation platforms but did see them while hiking on the dirt footpath.
Natural Bridges State Beach was named for a three bridge structure that at one time stretched from the shore out into the ocean. The historic photo to the right shows the three window structure circa 1905. The bridges are composed of mudstone, a soft sedimentary rock that formed from ancient sea floor muds. This Santa Cruz mudstone is composed of fine-grained silts, clays and diatoms which formed off shore 7-9 million years ago.
Natural bridges typically form from narrow peninsulas where waves bend around the headland and erode the sides of the rock outcrop. Often caves are formed which eventually erode completely through forming a window. Continued erosion eventually causes sections of the bridge to collapse. The outermost section of these natural bridges collapsed around 1906, and the inner most section collapsed during a storm in 1980. The middle section, now technically an arch, is what we see today.
In addition to the scenic arch, there are rocky tide pools and many shorebirds and aquatic birds to observe on the beach. These snowy egrets were humorous to watch as they played in the surf near sunset.