[nfc-l] Etna, NY: Night Migration Followup for 8-9 September

[Christopher T. Tessaglia-Hymes]

A quick observational browse through last night's recording data results in 
these highlights:

4 Black-billed Cuckoos
2 Hooded Warblers
1 Black-and-white Warbler
2 Lincoln's/Swamp Sparrows

Nothing really Earth-shattering as far as rarity, but it was definitely an 
active night.

Recently, I've been resting at night with a single earbud headphone plugged 
into one ear in order to listen in on the general nighttime activity. Last 
night, there were tons of calls from about 9pm through about 2am, then a 
gradual tapering to only sporadic calls the rest of the night. The morning 
thrush descent was very minimal at my location. There was one small descending 
flock around 5:34am, which included some Rose-breasted Grosbeak calls. There 
were some very distant thrush calls around 5:50-ish and a single close flyover 
Rose-breasted Grosbeak calling around 6:05am, but everything was pretty much 
shut down by 6:00am.

Thrush descent can be entirely hit-or-miss depending upon where the birds are 
during migration, just before the start of morning civil twilight (today it was 
at 6:10am).

I'd say that Rose-breasted Grosbeak was the species that dominated the night, 
followed by Swainson's Thrush. Early in the night, there was also a good 
passage of Green Herons. Throughout the night there were several Chestnut-sided 
Warblers.

After listening to the recent nights' migrations, I have been wondering about 
vocal activity vs actual birds in flight. Early in the night, birds are calling 
– seemingly everywhere. By the latter part of the night migration, vocal 
activity seriously drops off.

Why is this? I mean, even after a very quiet latter 3 1/2 hours, we can have a 
surprisingly actively vocal thrush descent. What is the theory for decreased 
contact/NFC calls as the night wears on? Are they all established in their 
individual flight patterns in the sky? Are they conserving energy by not 
vocalizing? Is there a relationship between very cold nights and decreased 
calling rates vs warm nights and consistent calling rates? If birds were 
descending earlier in the night we should observe decreased target density on 
RADAR; however, as Dave Nicosia mentioned, RADAR was still displaying active 
targets in the air as of 6am at our local station (BGM). Is there a generally 
accepted theory for decreased vocal activity into the night?

It has been fascinating to listen to and observe the gradual exodus of 
neotropical and other migrants from northern North America.

Thanks for any insight and good night-listening!

Sincerely,
Chris T-H

--
Christopher T. Tessaglia-Hymes
Field Applications Engineer
Bioacoustics Research Program, Cornell Lab of Ornithology
159 Sapsucker Woods Road, Ithaca, New York 14850
W: 607-254-2418   M: 607-351-5740   F: 607-254-1132
http://www.birds.cornell.edu/brp


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Re: [nfc-l] Etna, NY: Night Migration Followup for 8-9 September

[Andrew Albright]

"What is the theory for decreased contact/NFC calls as the night wears on?"

I thought one hypothesis(?) was that in the middle of the night the birds
are actually too high to be able to hear?

Has anyone ever tested empirically what elevation birds migrate at?   I
would think this would be relatively easy to do by placing several
microphones at different elevations on large manmade structures
(turbines/radio towers) or the top of ridge/valley and then compare how
loud the nfc calls are.

Some of this might already be published.
On Mon, Sep 9, 2013 at 12:01 PM, Christopher T. Tessaglia-Hymes <
c...@cornell.edu> wrote:

> A quick observational browse through last night's recording data results
> in these highlights:
>
> 4 Black-billed Cuckoos
> 2 Hooded Warblers
> 1 Black-and-white Warbler
> 2 Lincoln's/Swamp Sparrows
>
> Nothing really Earth-shattering as far as rarity, but it was definitely an
> active night.
>
> Recently, I've been resting at night with a single earbud headphone
> plugged into one ear in order to listen in on the general nighttime
> activity. Last night, there were tons of calls from about 9pm through about
> 2am, then a gradual tapering to only sporadic calls the rest of the night.
> The morning thrush descent was very minimal at my location. There was one
> small descending flock around 5:34am, which included some Rose-breasted
> Grosbeak calls. There were some very distant thrush calls around 5:50-ish
> and a single close flyover Rose-breasted Grosbeak calling around 6:05am,
> but everything was pretty much shut down by 6:00am.
>
> Thrush descent can be entirely hit-or-miss depending upon where the birds
> are during migration, just before the start of morning civil twilight
> (today it was at 6:10am).
>
> I'd say that Rose-breasted Grosbeak was the species that dominated the
> night, followed by Swainson's Thrush. Early in the night, there was also a
> good passage of Green Herons. Throughout the night there were several
> Chestnut-sided Warblers.
>
> After listening to the recent nights' migrations, I have been wondering
> about vocal activity vs actual birds in flight. Early in the night, birds
> are calling – seemingly everywhere. By the latter part of the night
> migration, vocal activity seriously drops off.
>
> Why is this? I mean, even after a very quiet latter 3 1/2 hours, we can
> have a surprisingly actively vocal thrush descent. What is the theory for
> decreased contact/NFC calls as the night wears on? Are they all established
> in their individual flight patterns in the sky? Are they conserving energy
> by not vocalizing? Is there a relationship between very cold nights and
> decreased calling rates vs warm nights and consistent calling rates? If
> birds were descending earlier in the night we should observe decreased
> target density on RADAR; however, as Dave Nicosia mentioned, RADAR was
> still displaying active targets in the air as of 6am at our local station
> (BGM). Is there a generally accepted theory for decreased vocal activity
> into the night?
>
> It has been fascinating to listen to and observe the gradual exodus of
> neotropical and other migrants from northern North America.
>
> Thanks for any insight and good night-listening!
>
> Sincerely,
> Chris T-H
>
>   --
> Christopher T. Tessaglia-Hymes
> Field Applications Engineer
> Bioacoustics Research Program, Cornell Lab of Ornithology
> 159 Sapsucker Woods Road, Ithaca, New York 14850
> W: 607-254-2418   M: 607-351-5740   F: 607-254-1132
> http://www.birds.cornell.edu/brp
>
> --
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[nfc-l] Thrush Migration 5-6 am this morning 9/9

[david nicosia]

Got up at 5 am and listened for night calls, particularly thrushes,
and found a decent flight, especially as they descended between
540 am and 555 am. During this time there were so many
thrushes coming down that it was hard to count so I just
estimated my numbers. Many times it was hard to tell if
it was the same bird calling more than once. 
I did have 3 separate GRAY-CHEEKED THRUSHES
at different times all very low. One was right over
the house and sounded like it circled. As expected
most thrushes were SWAINSON'S and I estimated about 60.

VEERY was about 20 and WOOD THRUSH about 10 or so. 

By 600 am I think it was mostly over but it was hard to tell from
increased traffic. Radar still showed some echoes
so it could have continued further. 

Good birding to all. 

Dave Nicosia 
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