A 24-year-old Willits woman calling herself "Warbler" has spent the past 18 days perched high in a pine tree just south of Willits.
The 60-foot tree is one of dozens marked for removal for the construction of a Highway 101 bypass around Willits.
Warbler, whose real name is Amanda Senseman, is among perhaps 100 protesters seeking to block construction because of concerns about the destruction of trees and wetlands.
"I'm not coming down unless the bypass is canceled altogether," said Senseman, a Willits-area organic farmer originally from Colorado. "I won't compromise."
Work on the bypass, which would eliminate a long-standing traffic chokepoint on the North Coast's major north-south route, is to begin at the end of the month, said Phil Frisbie, a Mendocino County Caltrans official.
"We've been fully respectful of the rights of citizens to peacefully and lawfully congregate, but she is trespassing in a construction zone," he said.
The first overt confrontation could occur next week. Caltrans on Tuesday received the final approval needed to begin construction, Frisbie said. In preparation, the agency plans to install a gate early next week to block off the area containing the tree where Senseman sits.
The protest group, called Save Little Lake Valley, is supporting Senseman's efforts by sending up meals on a pulley system and by holding weekly vigils at the site.
"It's been rather a luxurious tree sit," Senseman said. "The weather has been amazing, (although) it did rain a day and night, so it definitely motivated me to rig up my tarps better."
Tree sitting emerged as a form of environmental protest in the late 1980s. Julia "Butterfly" Hill gained international attention when she spent 738 days in a redwood tree in Humboldt County to protest clear-cutting operations. The protest ended peacefully in December 1999 in a settlement with Pacific Lumber Co.