Millions of monarch butterflies are passing through Chicago as part of their annual 3,000-mile migration

Dozens of monarch butterflies descended on the prairie at the Peggy Notebaert Nature Museum Tuesday, feasting on the nectar of purple ironweed flowers and golden compass plant blossoms.

The next day, monarchs flocked to the flame-colored Mexican sunflowers at a nearby community garden.

The iconic orange and black visitors were part of an annual spectacle: the late summer migration of millions of monarchs from as far north as Canada to wintering grounds in the mountains of Mexico, a journey of up to 3,000 miles.

“It’s already underway,” said Allen Lawrance, associate curator of entomology at the Peggy Notebaert Nature Museum. “They are passing through.”

Lawrance predicted that the migration will continue in the Chicago region for the next week or two.

There are many ways to experience the phenomenon. You can follow the monarchs’ surge at the Journey North website, a project of the University of Wisconsin at Madison Arboretum. You can also keep an eye out for orange wings when passing flowering plants such as zinnias, visit a nature preserve with monarch-tempting wildflowers or attend one of the region’s many monarch festivals.

The nature museum’s daylong festival on Saturday, Flutter into Fall, offers visitors a chance to see monarchs tagged and released, go for a guided plant and bug walk, or create a monarch-related craft with representatives from the National Museum of Mexican Art.

Recently listed as endangered by the influential International Union for Conservation of Nature Red List, monarchs have suffered from habitat depletion in general and the loss of wild milkweed in particular. Populations have shrunk by between 22% and 72% over the last decade, according to the group, which cited threats including logging in Mexico and California, herbicide and pesticide use, and climate change.

This year’s migration comes after a summer when members of local Facebook groups reported they were seeing fewer monarchs. Lawrance said very preliminary data from the nature museum’s Illinois Butterfly Monitoring Network also suggests a drop.

Monarch sightings were down 66% from 2021 in June and July, he said, perhaps due to some cold weeks in early spring.

“They seem to be down in the Midwest, but maybe the success in the East will make up for it this year. We’ll have to wait and see,” he said.

Lawrance said Chicagoans can help monarchs by planting milkweed, reducing herbicide and pesticide use, and planting flowers that bloom in fall. There are also opportunities to participate in community science projects that help monitor the butterflies at organizations such as the Illinois Butterfly Monitoring Network, Journey North or Monarch Watch.

“I’m not concerned about them in the immediate future,” Lawrance said. “But if nothing’s done for a long time, I’m kind of concerned about that.”