Mass Migration

Red admiral butterfly (photo by Daniel Herms, The Ohio State University,

Thursday, 19 April 2012

Last Friday I took the day off and visited Presque Isle State Park in Erie, Pennsylvania.  It felt like a mini beach vacation to walk along Lake Erie’s shore and pretend I was at the ocean.

With the waves lapping at my feet I paused to gaze north.  I knew that Long Point, Canada was more than 25 miles away but it was beyond the horizon … invisible.

Suddenly I noticed butterfly after butterfly flying from behind me and heading straight out over the open water.  They were brown, orange and white and they flew very fast, zigzagging on their way.

What was this steady stream of butterflies?  Red admirals!

Red admirals (Vanessa atalanta) live in temperate Europe, Asia and North America.  They cannot survive winter’s cold so they migrate south in the fall.  In the U.S. Red Admirals overwinter in south Texas.  In March they start their journey north.

How long would it take for these delicate creatures to cross Lake Erie?  I estimated I would have to run to keep up with them so I guessed they were traveling 7 miles per hour.  If they flew due north they’d reach Long Point in 3.5 hours, but they were headed northeast, a trip of 50 miles to the mainland of Canada.  This long route would take them more than seven hours.  It was 3:00pm.  They would arrive at night.

What I saw was only the beginning.  By Sunday the south winds and warm temperatures had triggered a mass migration.  From the Presque Isle Hawk Watch, Jerry McWilliams reported to PABIRDS:

“Probably the most remarkable observation was the mass movement of Red Admirals (Vanessa atalanta) flying SW to NE. A conservative estimate of the butterflies moving past the watch was 25 individuals per minute making the total estimate of the count around 5500 butterflies!”

The photo above matches what I saw.  The fall brood of Red Admirals is brown like this.  Those hatched in spring/summer are blacker.

(photo by Daniel Herms, The Ohio State University,

3 thoughts on “Mass Migration

  1. I’m glad I’m not the only one who thought the butterfly migration this week was pretty amazing! Sunday night I had about 100 of them swirling in little groups in my yard. It was the coolest thing when a few landed on me!

  2. I noticed it as well. I was wondering if I just never noticed it before, or it was some sign of the apocalypse or something.

    By my calculations, they were coming at a pace of about 500 per hour, and were probably twice that the other day!

    In the 6 minutes I counted I also saw 3 Monarchs and either an Eastern Question Mark or Eastern Comma.

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