Butterflies of Pier 94

By Ilana DeBare
We often talk about the bird life at Pier 94, the former waterfront dump site owned by the Port of San Francisco that we have been restoring as wildlife habitat since 2002. But Pier 94 is also becoming rich habitat for butterflies!
With support from a private family foundation, we contracted with San Francisco lepidopterist Liam O’Brien to conduct a year-long survey of butterflies, moths, and their host plants at Pier 94. Liam’s study took place from August 2016 through July 2017. We gathered additional data from a BioBlitz there in April 2017.
While we knew that some butterfly species were present at Pier 94, we were impressed by the range of species documented by Liam. Of 34 butterfly species found in San Francisco County, 20 were present at Pier 94.
The survey results  — in particular, which plants are hosts or nectar sources for our native butterfly species — are now informing our restoration work. This fall and winter, we’ll be planting specific plants to support butterflies, such as perennial grasses and deer weed in the upland area of the site.
Following are just a few of the butterfly and moth species Liam found. All photos by Liam O’Brien:

Anise Swallowtail is one of the butterflies found at Pier 94.
Anise Swallowtail (Papilio zelicaon) historically relied on native marsh plants such as angelica and cow parsnip, but today is found on the non-native fennel that dominates the edges of Pier 94.

Common Buckeye s one of the butterflies found at Pier 94.
Common Buckeye (Junonia coenia) is abundant during fall and can be found on native monkey flower and non-native English plantain.

Large Marble s one of the butterflies found at Pier 94.
Large Marble (Euchre ausonides) is a native butterfly often mistaken for a Cabbage White. Feeds on non-native mustards and wild radish.

Eastern-tailed Blue s one of the butterflies found at Pier 94.
Eastern-Tailed Blue (Cupido comyntas). This was only the second time Liam found this butterfly in San Francisco County; the first time was a decade ago at Fort Funston.

Ornate Tiger Moth s one of the butterflies and moths found at Pier 94.
Ornate Tiger Moth (Grammia ornate). The males are attracted to light, but females like this one can be found flying slowly during daylight.

Amon Blue s one of the butterflies found at Pier 94.
Acmon Blue (Plebejus acumen) hosts on perennial buckwheats and relies on coyote bush in the fall for nectar. Males are sky blue, females blue in spring and slate grey in fall. Both sexes have orange bands across their top hind wings.

Western Pygmy Blue is one of the butterflies found at Pier 94.
Western Pygmy Blue (Brephidium exile) is present all year. It hosts (lays eggs) on native salt marsh plants such as pickle weed and California sea blite.

Field Crescent is one of the butterflies found at Pier 94.
Field Crescent (Phyciodes pulchella). Liam was excited to find this one since its host, California aster, is rather sparse at Pier 94. He recommended planting more California aster to support this butterfly.

Venus is one of the butterflies and moths found at Pier 94.
Venusia, a genus of moths with five species in North America. It was unclear if host plants were present for breeding or if this moth was just passing through.

You can help make Pier 94 even more welcoming to butterflies, moths, birds, and other wildlife! Join one of our volunteer work sessions there on the first Saturday morning of every month. No prior experience needed; all ages welcome. Details and directions at goldengatebirdalliance.org/volunteer.