Millions of fire-orange and black monarch butterflies are heading south through the Chicago area, migrating from as far north as Canada to their winter home in the mountains of Mexico, the Chicago Tribune reports.
The annual late summer migratory path spans some 3,000 miles, and most butterflies arrive at their destination in November and stay until March.
The International Union for the Conservation of Nature, which maintains a “Red List” of endangered and threatened species, reports that monarchs have suffered from habitat depletion in general and the loss of wild milkweed in particular.
Populations have shrunk by between 22 and 72 percent over the last decade, according to the group, which lists several threats to their survival, such as logging in Mexico and California, herbicide and pesticide use, and climate change.
Although the monarch is on the Red List, the IUCN lists it as “Least Concern,” the lowest risk level for a species for which sufficient data has been collected.
“I’m not concerned about them in the immediate future,” the Tribune quoted Allen Lawrance, associate curator of entomology at the Peggy Notebaert Nature Museum, as saying. “But if nothing’s done for a long time, I’m kind of concerned about that.”
The Maryland Department of Natural Resources, in cooperation with Nature Watch, a citizen science group, has been “tagging” and releasing monarch butterflies in parks across the state for more than 20 years. Some of the tagged butterflies have even been found in Mexico.
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“In the fall, to help fuel the monarch butterfly’s amazing journey south to Mexico, it is important to have late-season blooming native plants for the adult butterflies to feed on, such as asters, New York ironweed, and goldenrod,” the department writes. “The nectar from these plants helps to feed the monarchs as they migrate south.”