Reader Joe Dickinson sent a photograph of one of the places where Monarch butterflies (Danaus plexippus) congregate for overwintering (larval and pupal stages cannot survive the cold of the northern U.S.). There are two main areas where they do this: northeast Mexico and southern California/Baja California; for a good overview of the process, see this website from the U.S. Forest Service. Here are the two main migration routes south:
Here are some shots from my annual visit to my favorite monarch “butterfly trees” in Santa Cruz (Lighthouse Field rather than the more famous Natural Bridges). To my eye, the population looks more robust than over the last couple of years. Dare one hope that that is a trend?
Here’s a video (not Joe’s) of the butterflies at Lighthouse Field: