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In Search of an Elusive Butterfly: the San Bruno Elfin

  • San Bruno Mountain State Park: Meet @ Radio Tower Summit parking lot 555 Guadalupe Canyon Parkway Brisbane, CA, 94005 United States (map)
San Bruno elfin. Photo: Liam O'Brien

San Bruno elfin. Photo: Liam O'Brien

THE DATE OF THIS WALK HAS CHANGED! We are now using the rain date of Sat, March 18 from 11 am - 1 pm. 

We made this change because as of 3/9, only one butterfly was observed by Liam after a few days of field scouting. We're hoping that the later date will give the butterflies more time to get active. Thanks for your patience... nature is on it's own schedule!

This walk is limited to 25 attendees! Please RSVP on the Eventbrite page.

Sat. 3/18, 11 am - 1 pm
If one wakes up on walk day and it is raining/inclement or overcast, the walk is cancelled: no butterflies in this kind of weather. This is a  difficult butterfly to see since it flies early in the rainy season. 

Cost: Walk is FREE, but there is a $6-8 entrance fee to the park

Federally Listed as Endangered in 1976, the San Bruno Elfin (Callophrys mossii bayensis) is a nickel-sized, Burmese brown denizen of the top-most, rock outcrops of San
Bruno Mountain.

The butterfly is an exquisite study in browns: burnt sienna, mocha and russet, with grey thrown in.  It's host is Stonecrop (Sedum spathifolium), the plant the females lay their eggs on. The butterfly doesn't live much beyond this niche habitat. After many years of taking folks to see this creature, O'Brien has located a guaranteed spot. There may be other "Harbingers of Spring" around as well, such as the Coastal Green Hairstreaks & Brown Elfins.

Our walk leader is Liam O'Brien, a Bay Area Conservationist who lead a walk last year for CCNH to see the Sonoran Blues in Alum Rock Park. He lives in San Francisco and goes by the name "robberfly" on iNaturalist. He was awarded the 2014 Bay Nature Magazine "Environmental Educator" Award and his latest project, Operation Checkerspot, has just be green lit by Calif. Fish & Wildlife for the Presidio Trust.

Where to meet and what to bring:

Meet at San Bruno State Park (off Guadalupe Parkway, San Mateo County). Pay the entrance fee ( $6-$8) and continue through main entrance. Drive all the way up to the parking lot to Radio Tower Summit, which is a couple of miles beyond Entrance Kiosk. Drive up until you can't drive any further- we'll meet at the last parking lot at the summit. 

Bring a light lunch- we'll stop to take in some beautiful views from the summit after we walk around. 

This walk will be easy to moderate- please wear comfortable hiking / walking shoes. It can get cold on the summit, so dress in layers and bring a coat. Remember to bring sun protection, your own drinking water, snacks / lunch, a camera, and anything else you might need to stay comfortable. Also, bring binoculars so you can see these small butterflies more clearly! We have some to share if you don't have any.

This walk is limited to 25 attendees! Please RSVP on the Eventbrite page.