Mission Blue Butterfly Monitoring on Sign Hill

South San Francisco, CA  May 27, 2021 Submitted by Emma Lewis, Natural Resource Specialist

For three months, City College of San Francisco student Brittney Johansen surveyed Sign Hill weekly for mission blue butterflies.

Before Brittney’s scientific efforts, City staff knew very little about the mission blue butterflies on Sign Hill. Monitoring an endangered species’ population from year to year is crucial for our efforts. It helps us learn if our habitat restoration is working, and can also be used by other agencies to understand species-wide recovery.
Using mission blue butterfly eggs as a proxy for the population, Brittney spent the spring surveying Sign Hill for mission blue eggs. She counted hundreds of mission blue eggs over the season, showing off her talent for scientific observation! While Brittney is still analyzing this year’s data, the results look promising. Sign Hill appears to have a robust population of mission blue butterflies that are recovering after the devastating 2020 Diamond fire. Brittney will attend San Francisco State University next year. She hopes to continue her butterfly monitoring on Sign Hill in 2022 as a research project. Thanks, Brittney!

Above: Brittney counting eggs with daughter Sophia as time keeper



Nature Sightings on Sign Hill

Paintbrush (Castilleja sp.)


This spring, Parks staff documented their first observation of the charismatic paintbrush genus on Sign Hill! The beautiful purple owl’s-clover (Castilleja exserta) and its close relatives, are common on San Bruno Mountain. They, however, have been largely lost on Sign Hill due to the spread of invasive plants.
This tiny plant germinated following the removal of invasive thistle by volunteers. It suggests that there is a biodiverse native seed bank on Sign Hill ready to reveal itself!

Pacific Gopher Snake (Pituophis catenifer catenifer)

Gopher snakes are often found on Sign Hill, if you can see them despite their camouflage. These nonvenomous snakes have important roles as carnivores in the ecosystem!


Brownie Thistle (Cirsium quercetorum)

This prickly plant has a soft side, providing lots of nectar and pollen for pollinators! Brownie thistle is one of our few common native thistles in the Bay Area.


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Ryan Fleenor
Ryan Fleenor
2 years ago

I have that same butterfly all over on my property I believe. So So Sophia be happy.