| Every fall, monarch butterflies (Danaus plexippus) west of the Rocky Mountains migrate to the California coast for the winter. The monarch butterfly is currently under review by the United States Fish and Wildlife Service for possible listing under the federal Endangered Species Act. It is therefore crucial that habitat for this species be conserved and properly managed. We conducted a comprehensive survey of monarch butterfly overwintering sites in Santa Barbara County during the winter of 2016-2017 and completed standardized habitat assessments at 106 of the 130 surveyed sites. We compared habitat characteristics (topography, canopy cover, presence of water, etc.) between sites that did and did not have monarch aggregations. We also examined disturbances and threats to habitat at each site. Overwintering sites with clustering monarchs had more tree and shrub cover, less bare soil, lower average wind speeds, and higher relative humidity within the grove. The presence of eucalyptus leaf beetle was the most prevalent threat to all sites, followed by drought stress. Information on habitat characteristics and potential threats will inform overwintering habitat management decisions and allow for more effective habitat restoration. |