Every year, millions of monarch butterflies across the U.S. and Canada journey up to 3,000 miles southward to a few select areas outside of Mexico City, where they spend the winter roosting in evergreen trees. If you’ve noticed more of the bright orange winged insects out and about over the past few days, that’s because they’re starting to make their way over the Chicago area—though their numbers won’t top off until later this week.
“We’re seeing migratory behavior here in Chicago already, but the real peak of the migration appears to be in Wisconsin at the moment,” says Dr. Doug Taron, chief curator at the Peggy Notebaert Nature Museum.
When the migration numbers peak, viewers can spot butterflies clustered together in groups or resting in trees as they continue on their two-month journey to Mexico. You can still expect to see monarchs throughout Chicago for several weeks after peak migration, with numbers slowly tapering off until the end of the month. Want to try to spot them yourself? To start, Taron advises heading toward the lakefront.
“The lake functions as what’s called a migrant trap,” he explains. “[Monarchs] don’t want to fly out over water, so as they get pushed toward the lakefront, they kind of accumulate there.”
That makes places like Lincoln Park, Grant Park and the Peggy Notebaert Nature Museum especially good for spotting monarchs, though you can also look around areas along the Chicago River and smaller waterways—or even in your own backyard, especially if you have flowers in your garden. Though monarchs are usually associated with milkweed (and for good reason, since it’s the only plant their caterpillars can eat and where the butterflies lay eggs), they love to drink up the nectar of all blooming plants this time of year, like goldenrods and Joe-Pye weed.
“Pay attention to places where there are lots of flowers in bloom, because it's going to attract them to take nectar,” Taron says. “They're out and about flying during the day, and these are big butterflies. They've got about a four-inch to five-inch wingspan. And so they're kind of hard to miss.”
Those looking to learn even more about the butterflies can visit Lincoln Park on Sunday, September 12, when the Peggy Notebaert Nature Museum is hosting its annual Flutter into Fall event. The day-long celebration of monarchs and nature in autumn includes a butterfly tagging session, during which visitors can watch scientists capture and delicately place a tracking tag on the wings of migrating butterflies. The tags, which log information including the date and the sex of the butterfly, help researchers track migration numbers from year to year.
“Tags that have been put on my wings in Canada have been recovered in Mexico,” Taron says. “This is part of how we know that it's the same individuals making this entire journey.”
That tracking process is especially helpful as butterfly populations continue to decline across the U.S., in part due to the loss of natural habitat and climate change-related rising temperatures (recent research suggests that the latter factor is even more influential than previously believed, Taron says, as population declines have occurred most precipitously in hot areas like Texas). And if you want to do your part to contribute to butterfly conservation, consider stocking up on milkweed and other nectar-filled plants to fill your garden and give butterflies a little boost of nectar as they make their long trip south next season.