Butterflies a plenty at San Bruno Mountain

Ariel Cherbowsky Corkidi, the director of San Bruno Mountain Watch, a nonprofit dedicated to preserving the mountain and its species, said staff, the county and volunteers work to manage and monitor the butterfly’s habitat and the overall ecosystem on the mountain.

And over the years, its numbers have increased.

“The best time to catch a glimpse of the iridescent blue insect is March to early June,” Cherbowsky Corkidi said.

Every two years, the county assesses the butterfly’s population. The four endangered or threatened butterflies are the mission blue, callippe silverspot and San Bruno elfin. In 2022, the last time it was surveyed, the county recorded 180 mission blue butterflies. Comparatively, in 2019, it counted 157, according to the county.

For the past two decades, Hannah Ormshaw, assistant director of County Parks, said results from surveys showed the mission blue butterfly’s population is stable.

“We are not at the point yet where we are seeing that it’s increasing but it’s not decreasing either,” Ormshaw said. “Overall, for an endangered species, we would love to see the population increase and achieve species recovery but we see it as good news that the population is stable.”

There are three types of lupine plants the mission blue caterpillars will use as host plants: summer lupine, silver lupine and the varied lupine. The San Bruno Mountain Watch Nursery grows all of the native lupines to ensure adequate habitat is provided for the caterpillars to eat. Adult mission blue butterflies feast on the nectar of coast buckwheat, California phacelia and coyote mint, which the nursery also grows and plants in its habitat, he said.

The 2.41-acre park has nine different trails where hikers can catch a glimpse of the scenic views of the Bay Area and enjoy the native species. Carla Schoof, San Mateo County Parks spokeswoman, said the best time to visit the park is during spring when wildflowers are in bloom.

“I would say the people who know it know it and visit it frequently, and people driving on Highway 101 see it but don’t realize what it has to offer, it is a very different place,” Schoof said. “It will be a little cooler in the morning but the fog usually will burn off mid to late morning.”

For novice hikers, Saddle Loop Trail is a 2 mile hike that has a 153-foot elevation change. The trailhead can be accessed from the main parking area. The gravel road is open to hikers and equestrians. It passes through a eucalyptus grove, cyprus trees, open grasslands that is home to a diverse number of native birds and is excellent for raptor viewing. It also has great views of San Francisco and the Marin headlands, according to the county’s website.

The Summit Loop Trail can be accessed from the southeast side of Guadalupe Canyon Parkway from the main park entrance. It is one of the more popular hikes for its high elevation and panoramic views of the Bay Area and the ocean. The hike is 2 miles long and has an elevation change of 1,314 feet. Hikers on the All Trails website recently noted the trail gets slippery near the top of the summit and hikers should be careful.

“It’s a pretty spectacular viewing point,” Schoof said.

Saving the mountain

The park and its habitat nearly had a different fate. In the late ’60s, developers had plans to flatten the top of the mountain, create a neighborhood, use the excavated rocks to fill the Bay and create a city the size of Manhattan with the landfill, Cherbowsky Corkidi said.

“At that time it was an equity issue for the people in the north county. There wasn’t as much open space and the mountain was the best possible park for the people in the area, and that was why people fought it,” Cherbowsky Corkidi said.

It never transpired and a small group of community members started an initiative called Save San Bruno Mountain fought against developing the mountain. That same group eventually became San Bruno Mountain Watch. By 1978, it became a state-owned and county-managed park.

If you go

The park opens at 8 a.m. and closes at dusk. Schoof said visitors should go during the week and in the early morning when it’s less busy. First-time visitors should dress in layers and bring a hat, she added. It has a $6 vehicle entrance fee. Schoof advises people to not leave valuables in the car. The picnic area and restrooms are near the parking area. There are no dogs allowed at the park and bicycles are allowed only on the paved roads. A youth camp is available by reservation only. Visit smcgov.org/parks/san-bruno-mountain-state-county-park for more information.