Monarch Butterfly Migration News

Monarch Butterflies

Poised for Departure
March 16, 2017 by Elizabeth Howard

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

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

Visiting a Sanctuary

Spring migration begins every March in a flurry. The monarchs are in a race against time. They can't stay in Mexico any longer — but they can't move north too quickly either. The timing of the monarchs' spring migration must be precise. How do they know when to leave, and why do they go now?

Time to Go! Spring migration begins every March in a flurry. The monarchs are in a race against time. They can't stay in Mexico any longer — but they can't move north too quickly either. The timing of the monarchs' spring migration must be precise. How do they know when to leave, and why do they go now?

Fat is Falling Time is running out because the fat the monarchs stored for the winter is almost gone.

Time is running out because air temperatures are rising at the monarch colonies. As it gets warmer and warmer, the butterflies burn their remaining fat faster and faster.

Temperatures are Rising Time is running out because air temperatures are rising at the monarch colonies. As it gets warmer and warmer, the butterflies burn their remaining fat faster and faster.

Time is running out because the monarch's winter habitat is as dry as a bone by March. Mexico's dry season began when the monarchs arrived in November. Now the colonies are breaking up as the butterflies fly out in search of water.

Water is Scarce Time is running out because the monarch's winter habitat is as dry as a bone by March. Mexico's dry season began when the monarchs arrived in November. Now the colonies are breaking up as the butterflies fly out in search of water.

Monarchs are Mating Time is running out because mating begins as temperatures rise. Monarchs live for only a few weeks after they mate.

Time is running out because monarchs must lay their eggs on milkweed. Milkweed is the only food their young caterpillars can eat. Imagine how much milkweed millions of monarchs will need!

Monarchs Need Milkweed Time is running out because monarchs must lay their eggs on milkweed. Milkweed is the only food their young caterpillars can eat. Imagine how much milkweed millions of monarchs will need!

Meanwhile, habitat is changing across North America. Milkweed and flowers will soon grow in the north. The area in red shows where the monarchs will migrate. Look at how much space the monarchs can have!

Spring is Coming in the North Meanwhile, habitat is changing across North America. Milkweed and flowers will soon grow in the north. The area in red shows where the monarchs will migrate. Look at how much space the monarchs can have!

"The spring equinox is probably the trigger for monarchs to migrate," says Dr. Lincoln Brower. Day and night are 12 hours long on the spring equinox. The monarchs may use day length as a cue to migrate.

Sensing Change "The spring equinox is probably the trigger for monarchs to migrate," says Dr. Lincoln Brower. Day and night are 12 hours long on the spring equinox. The monarchs may use day length as a cue to migrate.

With only a few weeks to live, the monarchs are racing northward. They are carrying the seeds of the next generation. Will the monarch's breeding habitat be ready when the butterflies arrive?

Here Come the Monarchs! With only a few weeks to live, the monarchs are racing northward. They are carrying the seeds of the next generation. Will the monarch's breeding habitat be ready when the butterflies arrive?

Watch how your backyard habitat changes with the spring season. Monarchs seem to appear like magic when their habitat is ready. Watch for milkweed and monarchs. Report your first sightings of the season to Journey North.

Track Spring's Journey North Watch how your backyard habitat changes with the spring season. Monarchs seem to appear like magic when their habitat is ready. Watch for milkweed and monarchs. Report your first sightings of the season to Journey North.

Companion Resources

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.

What to Report	Adults report \| map \| list	Eggs report \| map \| list

Larvae report \| map \| list	Milkweed report \| map \| list	Other Observations report \| map \| list

Next March 23, 2017