A number of migrating species annually make their way through Marin, notably the California gray whales, passing by in mid-to-late March; they can swim more than 10,000 miles a year — the farthest migration of any mammal. But another wonder is the flight of the monarch butterfly: it’s thought to be the longest-distance insect migration on earth, and it’s been happening for thousands of years. Monarchs sense and avoid large bodies of water and tall mountains, traveling in cool valleys between mountains instead. Every fall the butterflies west of the Rockies move to coastal California, and Marin has its share of overwintering sites. Here are some places to find them in the county, according to visitmarin.org.
TERWILLIGER GROVE/ MUIR BEACH
Take Highway 101 to Highway 1, then turn at Pacific Way, at the Pelican Inn. Continue past the inn and look for steps leading up into the pine grove on the hill. It is best to park at Muir Beach and walk to the site. Look for butterflies near the top of the stairs.
The monarchs are spied in the eucalyptus around the bank of Highway 1 at the north end of town.
The Bolinas Monarch Butterfly Grove, a little-known coastal butterfly migration site, has one of the largest populations during winter layover. Find it by driving into Bolinas, turning right onto Park Avenue and right on Terrace Avenue; then park near the intersection with Marin Way (it might be unsigned, so use a map on your phone). The winged creatures hang out in the trees near this corner.