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September 2013

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From:
Dan Best <[log in to unmask]>
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Date:
Sat, 14 Sep 2013 14:00:45 -0400
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Preface:  Ethan Kistler's suggested reference on dragonfly migration, triggered by the widespread green darner swarming this past week, most notably Sept 11, was very informative.  It mentioned a relationship between such migratory swarms and kestrel migration.  My friend John Smallwood PhD of Montclair University in NJ, a terrific ornithology researcher (and instructor) and a recognized authority on the American kestrel comments below.

Begin forwarded message:

> 
> Hey Dan.
> 
> Interesting article, thanks.  It's hard to get good quantitative data on how kestrels might use migrating dragonflies as a food source, since observations seem to be mostly anecdotal.  Now and then I've seen both kestrels and merlins eating dragonflies while flying past hawk watches.  (The birds were flying, not me.)
> 
> The article mentions that the migration of first-year kestrels coincides with the dragonfly migration.  I do have good data for kestrel dates, and on average the young do indeed migrate before the adults, especially adult males.  That's related to the annual pre-basic molt in late summer early fall.  Adults have a complete molt, but young have only a partial first pre-basic molt, involving some-all of the body feathers, but not the expensive flight feathers which are fairly new and not much worn.
> 
> Probably not possible to prove this sort of thing, but I would guess that dragonflies are a happy coincidence, and that the main selective factor determining timing of migration in kestrels is competition for good winter territories.  They usually won't migrate while molting flight feathers, so the young are good to go when they can feed themselves efficiently, and adult females wait until they complete the flight feather molt.  Late molting adult females sometimes suspend their molt "rather" than arrive too late on the wintering grounds.  Adult males bring up the rear, since their duties at the nest (feeding the female and young) delay their molt.
> 
> Cheers,
> John
> 
> 
> > John:
> > 
> > Ohio experienced a major dragonfly migration today with swarms 
> > spotted across the state including our backyard. This happened 
> > 2 or 3 years ago too.
> > 
> > The following article, courtesy of uber young birder Ethan 
> > Kistler is the most informative I've seen to date on this poorly 
> > understood migration. Note the reference made to the 
> > relationship between dragonfly swarms and migrating kestrels: 
> > (http://www.loudounwildlife.org/HHMigrationDragonflies.htm.
> > Best to ya's
> > 
> > Dan
> >


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