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When monarchs roost

Monarchs roosting (Point Pelee, Ontario)
Credit: Darlene Burgess
Monarchs roosting (Point Pelee, Ontario)
  • Monarchs roosting (Point Pelee, Ontario)
  • Monarchs roosting (Point Pelee, Ontario)
  • Monarchs roosting (Point Pelee, Ontario)
When monarchs roost

It’s autumn, and monarchs are gradually heading south. During their migration they make stops, sometimes in large numbers. Let’s take a look at the astonishing phenomenon of monarch roosting.

Why do monarchs roost?

Unlike certain migratory birds such as geese, monarchs migrate by themselves. Since these butterflies fly only during the day, they make a stopover every evening and set off again the next morning, weather permitting. From the air, monarchs identify interesting sites, and since they’re all looking for the same thing, a number of them will end up in the same spots. At that point they can be counted by the dozen, or even by the hundred!

What makes a good migratory staging site?

First of all, monarchs look for an abundance of nectar. So they’ll be observed in places that are rich in nectar-producing plants. In eastern Canada, they are attracted to plants like the Canadian goldenrod and New England aster.

To spend the night, monarchs prefer being sheltered; they settle on the leaves of trees, under the wind. At our latitudes, they’re often observed on conifers and maples, whose foliage is especially dense. A preferred migratory stopover site therefore consists of nectar-producing plants in bloom and trees in sufficient quantity to block the wind.

Where can we see monarch roosts?

Certain spots are known for playing host to monarchs in large numbers every year. That’s the case with Point Pelee National Park in southern Ontario, which acts as a bottleneck for butterflies migrating along Lake Erie. They assemble there while waiting for a favorable wind to help them cross that large expanse of water.

However, the location of migratory stopovers also varies from year to year. The phenomenon isn’t rare, but it’s not well documented. In fact, if monarchs touch down at the end of the day and take off again the next morning, the odds are that roosts will go unnoticed! Nevertheless, every year hundreds of roosts are reported in Canada and in the United States to citizen-science programs like Mission Monarch and Journey North. If you happen to witness the phenomenon, tell us about it by sharing your observations on the Mission Monarch website!

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2 Comment(s)
Pam Ososky's picture
Pam Ososky

I will never forget when I was about 17 (about 45 years ago). I was driving through rural Pennsylvania at dusk and came across this huge tree covered with what I now know were monarchs. It was the most spectacular sight I had ever seen. I was by myself with no one to share it with and of course there were no cell phones at that time to take a picture, but the picture remains in my mind as vivid as ever! It wasn't until I began working in my little school which teaches about the monarchs all through the grades that I realized what I had seen. I am now an avid pollinator plant person with a huge 800 ft pollinator garden in the front of my little school and many more in my own gardens. This year has been the most monarchs I have seen come through and I am hopeful that it is because of the interest people are taking to protect our pollinators and butterflies!

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Thank you so much Pam for your testimony!

The Blog Team

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