India, Nov. 9 -- There are myriad extraordinary animal phenomena in the natural world, from the running of the salmon to the months-long hibernation of bears. But in California, it's the monarch migration that naturalists and citizen scientists alike are waiting for expectantly right now.

Many (but not all) monarchs migrate seasonally, seeking refuge from too-cold temperatures. In Western North America, monarchs fly south from Canada and the Pacific Northwest to overwinter in temperate spots along the California coast. Some come from colder regions west of the Rocky Mountains, too. The overwintering season in California is roughly October to February.

During this time, monarchs cluster together in packed colonies for warmth-in a good y...