Resident Monarch Populations on the Rise in California: What Does this Mean for the Western Migratory Population?

By Stephanie McKnight on 1 March 2021

Many people have been seeing and reporting fairly large numbers of monarchs, both adults and caterpillars, all winter long in gardens on the California Coast this year. Since there haven’t been any formal studies of the number of monarchs breeding during the winter in California in prior years, it is difficult to know if there is in fact an increase this year, or if people are paying more attention and reporting them more often. Some researchers have unpublished data to suggest that winter breeding is on the rise in California, but more data is needed. It may also be that as more people have amped up efforts to help monarchs, there is now more milkweed in gardens and urban areas for monarchs to use—especially in large urban centers.

Read the rest of this Xerces Society blog here.