2012 Dragonfly Swarm Project Year-End Report: Distribution of Swarms

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It was another great year of data collection for the Dragonfly Swarm Project!  I continue to be impressed by the number of people who participate in this project, especially as it’s hard to promote it  in the hopes that someone might see a swarm and most people actually find the project after they’ve already seen a dragonfly swarm.  Still, over 700 reports were made in 2012 and that’s pretty darned good!  So, what does that data tell us?  The next two posts will focus on what we can learn from the data so far.  Today, I present the long-awaited maps (I think this year’s maps took a year or two off my life with all the stress they caused…) and next week I’ll discuss some of the patterns that I’m seeing in the data after three seasons of data collection.  Let’s dive into that data!

Like last year, I’ve split the map data into two videos.  It’s easiest to see changes over time when the images I create are presented as a series, so each map you’ll see in these videos represents the swarms that occurred during the time frame indicated at the top of the screen.  The pushpin colors mean something too: red represents a static swarm and blue represents a migratory swarm.  My apologies that the blue pins are a little hard to see on the map – they show up easily in Google Earth, but not so well in the images it produces.  For the best viewing experience, try watching the videos in full screen mode by clicking on the icon with the four arrows in the bottom right corner of the video player.  You’ll be able to see the changes from week to week more easily that way.

The first set of maps document the cumulative data for the year and show the overall pattern of swarm locations in 2012.  Each week’s new sightings are added to the previous weeks’:

The second set of maps shows the data for each month individually and by swarm type.  The first set of maps are the static swarms and the second are the migratory.  Each map represents only the data for the month indicated at the top of the video rather than showing the cumulative data.  For the migratory swarms, look closely along the southeastern and east coasts.  The pushpins are hard to see against the blue water of the ocean:

As you can see, there were once again more swarms reported east of the Missouri River than west of it.  In spite of the fact that Colorado made it into the 5 states with the most reports in 2012, there just aren’t that many dragonfly swarms in the west and some states (Montana, Wyoming, New Mexico) were entirely unrepresented this year.   Dragonfly swarms definitely appear to be more common in the east than the west.

In 2010, the center of activity was the western Great Lakes states and Iowa and last year it was the Pennsylvania/Ohio area.  This year, the activity was heaviest in the New Jersey area and northern New England coast in the mid to late summer and around the Chicago area in the late summer.   Each year seems to have a different center of activity, and I have a hypothesis for why this happens.  I’ll get to that in the next year-end report!

This year was an odd migration year.  The migration down the east coast has been documented several times in various publications, so it’s a fairly well-established route.  This year, there were very few reports of migratory movements in the east during the typical migration season in late August and September.  In fact, there were hardly any!  While most of the migratory movements reported this year did occur in the usual place, within a few miles of the coastline, the timing was all wrong: most were observed in June and July, much too early for the usual migration.  Again, I have a hypothesis that might explain this, but you’ll have to wait until next time.

The migration along the west coast was also quite weak this year.  That migration has a known set of conditions associated with it, a particular wind direction and a specific temperature.  The dragonfly people in Washington and Oregon were going out this year to the places they usually see migrating variegated meadowhawks on fall days with the right conditions and… nothing!  People were looking, and looking hard, so it seems that it was just a weak year for the migration overall, on both coasts.  I don’t even know how to explain the western migration fail though.  That’s just weird as that one is SO specific and occurs every year almost like clockwork!

Finally, I can say with more certainty that dragonfly swarms really aren’t a rare phenomenon and they happen more often than I’d ever expected when I started this project.  That is in keeping with the last two season’s worth of data.  However, last year I was uncertain whether I would continue to see an increase in the number of swarms reported every year and that has not been the case.  In 2010, I got about 650 reports.  Last year I got over 1100!  This year, I’m back down to 700.  I have a feeling that 600-800 swarm reports per year is normal and that the several hundred reports I got over a 3 week period last year were related to a set of perfect conditions that allowed a massive boom in dragonfly activity right toward the end of the year rather than an increase in participation in the project.  I’ll explain why I think that boom happened in the next part of the year-end report, but I predict that next year we’ll see the same sort of numbers we did this year, barring any sort of odd convergence of conditions that allow another 2011-style reporting boom.

If you’d like to see images of the maps of all the data for the year, I’ve uploaded them to my Yearly Maps page.  There, you can view the maps for static, migratory, and all swarms by year, which should make comparing between years fairly easy.  Click on the images to see a larger version of the map – they’re very tiny on the yearly maps page.

That’s it for this installment, but part three of the year-end report (the conclusions) will be up on Sunday.  It should be pretty interesting!

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Unless otherwise stated, all text, images, and video are copyright © C. L. Goforth

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Have you seen a dragonfly swarm? I am tracking swarms so I can learn more about this interesting behavior.  If you see one, I’d love to hear from you!  Please visit my Report a Dragonfly Swarm page to fill out the official report form.  It only takes a few minutes! Thanks!

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Want more information? Visit my dragonfly swarm information page for my entire collection of posts about dragonfly swarms!

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