Safe journey, monarchs!
- Jeanne McRight
- Oct 2
- 3 min read
Updated: Oct 3
by Jeanne McRight
What a sight! Today I walked along a path through a meadow of asters and goldenrods all a-flutter with dozens of nectaring monarchs. One of the many joys of early autumn is witnessing our migrating butterflies stoking up on the especially nutritious nectar of native asters and goldenrods, now blooming like crazy in empty lots, fields and meadows, roadsides – and gardens!
Monarchs on goldenrod and aster. Photo by Ellen Macdonald ˘
Did you know
A cluster or flock of butterflies is called a kaleidoscope.
The monarchs in our southern Ontario gardens are the great-great grandchildren of those that departed from this area last fall. They are very special. This final generation looks much the same as those previous, but its body works differently:
These monarchs are not able to reproduce until after their winter rest period (this is called a diapause) in Mexico. Instead, in fall it's their job to eat, bulk up, and fly.
Our fall monarchs can live for up to 9 months, as opposed to their spring and summer ancestors who live only 2 to 6 weeks.
They are the only generation that makes the 2,800 to 3,000 mile round trip, which makes them the long-distance champions of the butterfly world.
Why migrate?
Monarchs must migrate to escape our frigid winters, yet they need cold to slow down their metabolism, and humidity to maintain a state of energy-saving dormancy (diapause). The humid microclimate of their wintering grounds, found in the oyamel fir forests of Mexico, allows them to survive until spring without having to use precious fat reserves to combat desiccation. The fat reserves allow them to start their journey north in the spring.
What Triggers Migration
Environmental Cues: The primary triggers are the changes in the environment that occur in late summer and early fall.
Decreasing Day Length: The shortening days signal the approaching winter.
Temperature Drops: Cooler temperatures also contribute to the cue for migration.
Aging Milkweed: Milkweed is monarch caterpillars' only food source, and the aging of these plants in the fall coincides with the emergence of monarch's final generation – those who migrate instead of breeding.
Roosting: These monarchs begin to mass in clusters called roosts, which signal the start of fall migration. They begin to fly in the morning after warming up their muscles in the sunshine. Using the sun as a compass and the lift of warm air currents to conserve energy, they fly south independantly during the day. As the land cools in the afternoon, the warm air currents end, causing monarchs to come down from the sky to feed, and they roost communally at night in trees.
Roosting monarchs. Photo by Jessica Bolser/USFWSmidwest, Public domain, via Wikimedia Commons
Where to see migrating monarchs:
Monarchs frequently congregate along the Lake Ontario and Lake Erie shorelines, especially in the evenings, to rest and wait for favourable winds to cross the lakes. Presqu’ile on Lake Ontario and Point Pelee on Lake Erie are especially important resting spots for monarchs before they cross.
Tips for Spotting Roosts
Timing:
Arrive an hour or two before dusk or just after sunrise to catch monarchs congregating or taking off.
Conditions:
Warm days with winds from the north are ideal for monarchs to fly south
Seeing monarchs?
Your sightings can help citizen science organizations such as Monarch Watch and Journey North present balanced and accurate reports of where monarchs are appearing each week. Your detailed description of what you see can include adult monarchs, eggs, and larvae, as well as the monarch’s gender and activity. If known, include the type of flowers if they are nectaring or milkweed type if laying eggs. Photos are encouraged and welcomed with all your reports.
Check out Journey North's real-time map here https://maps.journeynorth.org/map/?map=monarch-adult-fall&year=2025
Check out Monarch Watch's migration map here https://monarchwatch.org/migration/
Sources
Migration and Overwintering U.S. Forest Service
THE INTERNATIONAL MONARCH MONITORING BLITZ is a call to action for individuals, organizations and community scientists across North America International to join efforts to conserve monarch butterflies and the habitat they depend upon. https://www.cec.org/wp-content/uploads/CEC-Monarch-Monitoring-Blitz.pdf
View monarch migration tracked on Journey North here https://maps.journeynorth.org/map/?map=monarch-peak-migration&year=2025
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