Poised for Departure
March 16, 2017 by Elizabeth Howard

Millions of monarchs are poised to leave Mexico and a gradual departure is already underway.

Monarch Butterflies at Cerro Pelon winter sanctuary in Mexico

Flitting about the stalks of yellow jara blossoms (Barkleyanthus salicifolius), fueling up for their journey.
Dr. Ellen Sharp Cerro Pelon Sanctuary March 14, 2017

Signs of Departure
"Monarchs must be creeping northwards day by day," Estela concluded after visiting El Rosario and Chincua on March 13th and 14th. Full departure occurs sometime during the last half of March. It can be sudden and dramatic or almost imperceptible.

Winter has taken its toll on the butterflies, as Estela's observations show:

"Many monarchs have now lost their bright orange colour, many others make a fly-walk at ground level seeming indeed weak now, certainly not able to make it north in a few days. A few of them try their best with tattered wings. The season heads inevitably to its end." Read more...

The Long Goodbye
At Cerro Pelon, Ellen Sharp is also noticing a slow, gradual departure. The colony looks subtly diminished every day.

"Maybe this gradual leave-taking is a good thing, because spreading themselves out limits the damage that one bad weather event could do to the monarchs....It now seems that it is just a matter of days that they will still be with us." Read more...

Time to Go!
The first day of spring is March 20th. When will the remaining monarchs head north?

"The spring equinox is probably the trigger for monarchs to migrate," says Dr. Lincoln Brower.

Monarch butterfly at sanctuary in Mexico in snow.
Letter from Estela
Monarch Butterflies Mating in Mexico Before Departure
Letter from Ellen Sharp at Cerro Pelon

Monarch Butterflies at sanctuary in Mexico
Milkweed Emerging

Spring Migration: A Race Against Time

Companion Resources

Timing of Spring Migration


Photo Gallery

Text Only Article

Teaching Suggestions

Driving Question

By the end of March, the monarchs can't stay in Mexico any longer — but they can't move north too quickly either. What changes are occurring in the butterflies and in their habitat?

Report Your Sightings
Report all monarchs you see — adults, eggs, larvae.
Monarch butterfly migration map Monarch butterfly migration map Monarch butterfly migration map
What to Report Adults
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Monarch butterfly migration map Map of milkweed emergence: Spring 2017 Monarch butterfly migration map
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Other Observations
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Next March 23, 2017