(Editor's Note: this article was originally published on November 24, 2008. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
Western monarch butterflies spend the winter near the coast from Marin County to San Diego County. (Possibly there are some in Baja California, Mexico, but the information is conflicting.) They spend the winter in populations ranging from hundreds to hundreds of thousands, depending on the site and the year. They stay near the coast where the ocean water tempers the night air temperature. However, they stay inland just a little to avoid the brunt of winter storms. They roost in groves of trees, the whole colony roosting close together to conserve heat. Tens of thousands of butterflies may spend the night in an area of little more than an acre. Their favored trees are Monterey pines, eucalyptus, Monterey cypress, and redwoods.
The spring and summer generations of monarchs live for about six weeks. However, the wintering generation can live up to eight months. This last generation is born in late summer or early fall and the decreasing daylight causes the adults to not reach full sexual maturity and also signals them to migrate. Some of the rugged little creatures travel from as far away as Canada. In the spring, the increasing daylight allows the butterflies to reach sexual maturity and begin migrating north and east. Migration starts in February or March. The wintering adults lay eggs where they find milkweed and thus start the next generation. Some of this next generation will continue the migration north. This continues on for up to five generations. The individual monarchs at a wintering site have never been there before. Most of these individuals will not make it back to their place of birth, either.
During the day the wintering butterflies fly around, but there are always many roosting in groups at any one time. They rest with their wings closed, showing the relatively dull undersides of their wings and look a lot like dried leaves.
The monarch population varies from year to year and appears to be dependant on the abundance of milkweed in the summer. That in turn is dependant on weather and land use. Probably the most famous U.S. wintering site is Pacific Grove, California, the self-proclaimed "Butterfly Town, U.S.A.", but the California Department of Fish and Game recognizes approximately 80 wintering sites. Some of the sites include:
The site with which I am the most familiar is Pismo Beach. We have gone there many times, usually between Thanksgiving and Christmas. Strange as it may sound, because of that, I tend to associate monarchs with Christmas. Using some imagination, you can see some connections, though. Orange and black my not be classic Christmas colors, but the distinctly-veined wings remind me of stained-glass windows and the human visitors' attitude is almost reverent. The absolutely silent insects flutter around like an orange snow flurry. The feeling is as magical as the Christmas season. There is peace on earth, or at least a tiny section of it. It is one of God's wonders.
Visiting the Pismo Beach site: Monarchs can be found here from late October to February. Over the past 20 years, the annual population has varied from 17,000 to 230,000. If you end up visiting during a lower population year, do not be dismayed. To tell you the truth, I can't tell the difference between a 17,000 member group and a 50,000 member group. The yearly population peak is right around Christmas. Monarchs cannot fly when the temperature is below 55 F. Try to visit on a warm day, and most days will be warm.
During monarch season, the grove is staffed every day by volunteers who are ready to answer your questions. They give talks at 11 a.m. and 2 p.m.. They have a few small displays like a monarch population chart and live monarch caterpillars. You will find a couple spotting scopes in the grove that the volunteers have aimed at roosting clusters of butterflies. Do not touch the scope. The focus and direction have already been adjusted. Near the grove is also a small trailer where they sell souvenirs and educational materials.
The grove is right by the street (Pacific Coast Highway), about 1/4 mile south of the North Beach Campground entrance. Park on either side of the road. There is space to pull off the road. I do not know much about the subject of handicapped access, but I would say that the grove is handicapped accessible in a general sense. The site is flat, though the parking area and trail are not paved. There are no picnic areas, food and beverage sales, water fountains, or restrooms right at the grove. There are restrooms and water in the campground, roughly 1/4 mile down the trail from the grove. It is about 1/3 mile from the grove to the beach itself. Chances are you'll find the ocean water too cold for swimming during butterfly season, but the hard sand is great for walking. The town of Pismo Beach lives off of tourism, so you'll find a variety of restaurants and hotels nearby.
If you are in California in the fall or winter and are near the coast, consider a visit to one of the aforementioned parks. The parks are attractive in their own right and the butterflies make them that much more charming. A visit will certainly be worth your effort.