Monarch butterflies clustered on eucalyptus tree (Photo by Kathy Riley)

Each year, thousands of monarch butterflies from across the west make their way to the California coast where they spend their winter, including making migratory stops at East Bay parks. For the past two decades, volunteer citizen scientists have been counting them during the Annual Western Monarch Thanksgiving Count, organized by the Xerces Society. Christina Garcia, a naturalist at the East Bay Regional Park District, has been counting butterflies at Ardenwood Historic Farm in Fremont for over 20 years. This year she spotted 66 butterflies compared to 25,000 when the count began in 1997. The trend at Ardenwood is playing out throughout the state; the number of overwintering monarch butterflies in California dropped 86 percent since last year, according to the annual count.