Bringing Back The Bay Checkerspot Butterfly


An ongoing priority for the San Mateo County Parks Foundation is to re-establish the federally-listed Bay Checkerspot butterfly at Edgewood Park and Natural Preserve. This butterfly is found in rare serpentine soils in only two counties in California.

Since 2007, the Parks Foundation has been working with a team of scientists, volunteers and partners to restore native plant habitat and re-introduce the butterfly to its former home.

Bay Checkerspot Butterfly

On the edge of survival: the presence of the threatened Bay Checkerspot butterfly is one of the reasons Edgewood Park became a natural preserve instead of a golf course! Checkerspot caterpillars eat California plantain and owl’s clover, while adult butterflies sip nectar from wildflowers like goldfields and tidy tips — all native plants found at Edgewood. However, invasive, non-native plants are crowding out the plants the butterflies depend on.


Bay Checkerspot Butterfly Re-Establishment Elements

  • Larvae and adult butterflies are transferred from a population on Coyote Ridge in Santa Clara County to Edgewood Park
  • Over the course of the butterflies’ flight season, trained volunteer “citizen scientists” (checker-spotters) survey adult butterflies daily, walking established transects and recording the number of butterflies observed
  • Habitat restoration efforts include well-timed mowing of annual grasses and fall dethatching to reduce grass cover and increase host and nectar source plants. Volunteer Weed Warriors help through hand pulling and other labor intensive work, drastically reducing grassland weeds such as yellow starthistle, Italian thistle and teasel and preventing establishment of new invaders like stinkwort and Mexican feather grass.

Check out our educational videos about Edgewood Park and Natural Preserve:

Our Partners: San Mateo County Parks, Creekside Center for Earth Observation, the U.S. Fish and Wildlife Service, California Native Plant Society, Friends of Edgewood, and Pacific Gas and Electric Company


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