This year’s Western Monarch Thanksgiving Count show the monarch population continues to decline. The challenging fall and winter seasons of unseasonably warm temperatures may have caused monarchs to arrive at overwintering sites later. California wildfires, smoke and mudslides may have affected late season migrating and breeding monarchs as well.
The Xerces Society for Invertebrate Conservation tells us “monarch butterflies that spend the winter within forested groves along California’s central coast are born on milkweed throughout western states, traveling to the coast from as far away as Arizona, Utah, Idaho, and Washington. The western population of monarchs has undergone a long term decline that mirrors the trend observed at overwintering sites in the mountains of central Mexico, where monarchs from both the eastern and western U.S. also spend the winter.” (Xerces)