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A new stretch of trail in the Pulgas Ridge Open Space District in San Carlos on May 13, 2024. Photo by Angela Swartz. 
A new stretch of trail in the Pulgas Ridge Open Space District in San Carlos on May 13, 2024. Photo by Angela Swartz. 
A new stretch of trail in the Pulgas Ridge Open Space District in San Carlos on May 13, 2024. Photo by Angela Swartz.
A few weeks ago a new, 630-foot-long trail was opened up near the northwest section of the Pulgas Ridge Open Space Preserve.
The unnamed trail provides a new public access point of entry into the preserve, at the end of Los Vientos Way in the city of San Carlos.
Before the trail was created, Midpeninsula Regional Open Space District ecologists worked hard to ensure the Bay checkerspot butterfly, an endangered species, would not be adversely impacted in the process.
Their work involved a thorough search for this type of butterfly along the length of what is now the completed trail. To this end, two surveys were conducted this spring, one in March and another in April.
“Before we (did) any sort of work, we wanted to see what natural resources we have at the site that we want to protect,” said Coty Sifuentes-Winter, supervisory vegetation ecologist for the district, in an interview with The Almanac. “Part of our mission at Midpen is to protect and restore the natural environment.”
Factors that endanger the Bay checkerspot butterfly include a combination of habitat fragmentation, which occurs when roads and freeways are built in the middle of their natural habitat, and car pollutants.
To thrive, the Bay checkerspot butterfly requires a certain type of environment — serpentine grassland, which comprises a special kind of rock that tends to be rich in heavy metals and low in nutrients.
“Although we don’t have serpentine at this location, which is sort of the requirement of the butterfly, it does have the host plant and it is very close to Edgewood which we know has the butterfly,” Sifuentes-Winter said.
The butterfly’s host plant is the dwarf plantain, scientifically known as plantago erecta (commonly known as the dot-seed plantain or California plantain), which is where it lays its eggs and rears its young. Once the eggs hatch they feed on the host plant before going through several other stages in their lifecycle that require them to be near the plant.
“So we actually wanted to get out to the site and verify that it (the butterfly) wasn’t present. The objective was to make sure it wasn’t there,” he said. “If it was there then we would want to change our design of what this trail might look like and how we’d do the work there.”
For instance, if they had found the butterfly, they might have considered using hand tools instead of big machines or creating a seasonal trail, he said.
The survey is known as a “butterfly transect walk,” a process that Sifuentes-Winter carried out with eight other biologists. They all went to the site and walked along the path at a certain pace and counted the butterflies they spotted along the way and classified them by type.
Last fall, when they were thinking of opening up a trail at this location, the team conducted a similar search specifically for the butterfly’s host plant. At the time, Sifuentes-Winter did what he calls a “forensic botany,” or a search for the dead host plant, which is an annual plant, which means it grows and dies every year.
And he did find it. “So we got verification that the host plant is there,” he said.
But the butterfly was not there. To be sure of this, it was important to carry out the search in warm, sunny weather, because that’s when the butterflies come out. A search in wet, windy weather that does not yield any butterflies does not necessarily mean they aren’t there; it could simply mean they’re hiding. That’s why an important tool in their search mission is a hand-held weather station that reads the wind, temperature and humidity.
They also did a review of the host plant to check whether the butterfly had laid eggs and was eating it. “The dwarf plantain is really small — it could be anywhere from 1-inch tall to up to 2 or 3 inches tall, so you’re down on your belly looking for tell-tale signs that it is being eaten,” he said.
Sifuentes-Winter, who grew up in rural Idaho, has been in the Bay Area for 25 years. He was inspired to get into this line of work since he first beheld a park ranger at the age of 5. His ambition was cemented a few years later when he watched “Never Cry Wolf,” a Disney movie about a biologist’s adventures in the Arctic. Before coming to Midpen he worked for the National Park Service for several years.
“I get paid to play in the mud and count flowers,” he said.
