The Stages of Migration
Migration season in North America has begun, and the dragonflies are assembling in mass flights. The earliest migration report came to us from Cape May, where winds out of the north on July 24 brought huge numbers of Swamp Darners (Epiaeschna heros) and other dragonflies, many of which ended up in the beaks of Purple Martins. Swamp Darners were also among the earliest southward dragonfly migration reports in 2012, raising the possibility that this species may be an annual migrant, at least in the northeast.

The usual suspects have also been on the move. In the east, swarms of Wandering Gliders and Spot-Winged Gliders (Pantala flavescens and P. hymenaea), along with a few unspecified Saddlebags (Tramea spp.), were on the move in Massachusetts in early August--but heading north. A look at the map suggests they may have been trying to cross Plum Island Sound and Ipswich Bay while covering the smallest expanse of open water, although we don't know for sure.

Late August saw reports of late-season Black Saddlebags (Tramea lacerata) in southern Quebec at the St. Lazare sand pits, where they have been seen annually in late August/early September for the past five years. Are these the offspring of spring migrants, destined to fly south for the winter? Even more notable at this site was the presence of newly-emerged Variegated Meadowhawks (Sympetrum corruptum) beginning in late July. Prior to this, there were only two records for this species in the province--are these new residents, or the offspring of a prolific migrant?

Things have been a bit quieter further west, although substantial movements have been noted. The Smith Point Hawkwatch blog, which details everything on the wing around their Gulf Coast observatory in Texas, reported August flights of both regular and more sporadic migrants (Red Saddlebags [Tramea onusta], Blue Dashers [Pachydiplax longipennis], and Striped Saddlebags [Tramea calverti]). August 15-18 were particularly active days, with tens to hundreds of thousands of dragonflies migrating through along with the usual contingent of kites and hawks. These reports dovetail nicely with August 16th observations of a steady movement of hundreds to thousands of Common Green Darners in Sargent, Texas, about 120 miles further down the coast from Smith Point.


Other reports are a bit more puzzling. On August 24, there were large numbers of Black Saddlebags and Gliders "all over the road" along I-5 from Redding, California southward--could these have been migrants, following an easy inland corridor? Similarly, a non-directional flight of large numbers of Common Green Darners was reported in CA, over 100 miles inland from the Pacific Coast. This could have been just a feeding swarm, but the observer noted that no such numbers had been present for several days prior. We know that the concentrated flights along the coasts and through the Midwest have their origins in multiple places, but we know very little about how they originate. Was this a staging area for a larger flight awaiting the appropriate environmental cues for movement, or perhaps a rest stop for a flight that was already in motion, re-fuelling for the long journey ahead?

 

The only way to answer these questions is with regular observation and reporting from volunteers like you. So as summer fades into fall, keep making those Pond Watch visits, and keep your eyes on the skies--and the trees and fields and highways--for dragonfly swarms on the wing or near the ground. Happy dragonflying!

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MIGRATION DATA
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The Migratory Dragonfly Partnership is composed of dragonfly experts, nongovernmental programs, academic institutions, and federal agencies from the U.S., Mexico, and Canada. Together, we are combining research, citizen science, and education and outreach to better understand North America's migrating dragonflies and promote conservation of their wetland habitat. 
Photo Credit: Swamp Darner (Epiaeschna heros), Dennis Paulson

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