[CT Birds] day warbler migration?
gswilliams9 at yahoo.com
Thu Sep 24 14:01:00 EDT 2009
When I lived in Norwich, I was just north of Mohegan Park. My backyard bordered a large cemetery to the west that was pretty treeless. At about 5:00 pm in spring, warblers would begin to trickle throught the yard, sometimes in good numbers. All birds were actively feeding and moving north. I assumed that birds had settled into the city-surrounded green of Mohegan Park while migrating on favorable spring nights. They would then start to move north in daylight and stock up on food before undergoing nocturnal migration several hours later. These (mostly) warblers were clearly moving in a northern direction and the combination of being north of the park and having an open cemetery border, they concentrated along my yard. They also did this on the other side of the cemetery.
I have also noticed that spring hot spots such as East Rock Park fill up with birds after great migration conditions, but the birds do not remain there even if poor migration conditions exist a few days afterwads. I assume that the birds just gradually work their way north during the day and will again make a big flight when conditions are right.
Does any of the research about zugunruhe or "migratory restlessness" show that this desire to move in the appropriate migratory direction occurs to some degree in the day as well as night in nocturnal migrants?
--- On Thu, 9/24/09, David F Provencher <david.f.provencher at dom.com> wrote:
> From: David F Provencher <david.f.provencher at dom.com>
> Subject: Re: [CT Birds] day warbler migration?
> To: "CTBirds" <ctbirds at lists.ctbirding.org>
> Date: Thursday, September 24, 2009, 12:47 PM
> Paul what you were seeing is called
> "Morning Flight." I only have a moment or two so here is a
> brief description: It was discovered many years ago that
> nocturnal migrants (not all but many) do a brief period of
> continued migration in the early daylight hours. This the
> big push that happens at Bluff Point that you hear about in
> postings. I happened onto the concentration that occurs
> there years ago but I don't have time in this post to
> discuss the nuts and bolts. Suffice it to say that the
> nocturnal migrants come down to rest in the predawn. Then
> shortly after dawn they start moving again, hence "Morning
> flight." While nocturnal migration tends to be "Broad-front
> migration" or generally by compass heading, morning flight
> tends to be more "Leading Edge" migration, following
> ridgelines, coastlines, river valleys, etc. So what you saw
> were indeed Morning Flight migrants (well spotted by the
> way!) They will push on for about 1 to 2 hours then settle
> into foraging then resting by mid-day or early afternoon.
> Not all species do it, for instance Warbling Vireos are
> believed to largely not undertake morning flight. I will try
> and do a more detailed discussion post later this week or
> weekend but no promises since I plan to be hiking in the
> White Mountains on Saturday!
> To me, I felt these birds were doing a true migration
> during the day! We all know most passerines migrate during
> the night, but has it ever been seen that Warblers might
> just do some migration during the day hours?
> Would be interested in hearing any comment to
> Paul Carrier
> Dave Provencher
> Naturally New England<http://naturallynewengland.blogspot.com/>
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