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Fall Migration South

Click here for Spring Migration North

In the northern reaches of the eastern range of monarchs, the generation that ecloses in August remains sexually immature (in reproductive diapause). Rather than breeding like earlier generations, this generation nectars heavily on nearby flowers to increase lipids (fats) for several days. Then they take to the skies and begin their fall migration with directional flight south and southwest. This is usually first seen around August 15 in Winnepeg, Canada. As they fly they pick up new butterflies forming a wave in the central part of the United States. The migration of monarchs also occurs in the western United States but details are less well known. However, with Citizen Scientists reporting monarch sightings, monarch directional flight, and tagging migrating monarchs, we learn more every year.

Through tagging, we are continuing to learn more about the migration and destinations of monarchs in the southwest. During the Fall migration, small clusters have been documented in Lake Havasu City, Parker, and Canelo in Arizona. Tagged monarchs have been discovered at overwintering sites in both California and Mexico. Some also spend the winter in the lower deserts of Arizona and California. We look forward to more reports of monarch clusters from throughout the southwest.

When can you expect to see the most migrating monarchs? See Peak Migration.

We have learned that the migration window for the southwest is quite long, primarily from early September through October. There have also been two late season monarchs tagged in November that were seen in Kino Bay, Sonora, Mexico and Palm Desert, California respectively.

Monarchs reach their overwintering sites in California and Mexico near November 1st and continue arriving through the first week of December or later. They remain in clusters, not breeding, until Spring when the breeding cycle begins again. Breeding monarchs normally live about a month as adult butterflies, but migrating butterflies do not breed and so can live as long as eight months.

Fall Migration Map

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