The link is here: http://www.xeno-canto.org/discuss_forum.php?topic_nr=6401
The consensus was that based on the diurnal variation of calls "Gray-cheeked"
calls may be Bicknell's or Gray-cheeked.
Is it still safe to assume that "Bicknell's" calls are Bicknell's?
Another great flight last night, fourth in a row, hopefully more
Bicknell's-type calls in there!
Paul Driver
Elkins Park, PA
-----Original Message-----
From: Andrew Albright <[email protected]>
To: Christopher T. Tessaglia-Hymes <[email protected]>
Cc: <[email protected]> <[email protected]>; NFC-L <[email protected]>
Sent: Wed, Sep 25, 2013 10:00 pm
Subject: Re: [nfc-l] Migration 9/23-9/24 - HF Gray-cheeks
Paul or others - do you have the link to the xeno canto discussion?
Two years ago, we had some discussion here -
http://www.mail-archive.com/[email protected]/msg00509.html
There is some good information in that thread.
Without reading the xeno canto thread, it seems that there is an inbetween area
of either overlap between the two species and/or a subspecies (probably
Gray-Cheeked) that has the internmediate call.
Lastly, if the estimates of the population sizes are roughly correct
(Bicknell's at 100k and Gray-Cheeked at 12 million), then when in doubt is
safest to assume Gray-Cheeked.
On Wed, Sep 25, 2013 at 6:00 PM, Christopher T. Tessaglia-Hymes
<[email protected]> wrote:
Hi Paul,
Thanks for commenting. Your examples are fantastic. All starting abruptly and
peaking almost at 5kHz. The "candidate" examples I provided were peaking
between 4.7 and 5.0 kHz; however, it seems, none of them were sufficiently
outside the range of suspected HF Gray-cheeked Thrush-type calls.
I agree, we don't know enough about the nocturnal vocalizations of Bicknell's
and Gray-cheeked Thrushes to safely rule out some of these HF candidate calls
away from being Bicknell's or to confidently ID them as Bicknell's. We simply
don't know how much true overlap there may be, especially when considering the
individual variation between adults and juveniles, and males and females,
during fall migration. Spring migration, presumably, we would only be
considering male and female variations and could rule out the variability
between adults and juveniles.
Ideally, we would have recording stations located near or on a direct flight
path South or Southeast of their breeding grounds to collect more likely
candidates as comparison.
Most of my recorded Gray-cheeked Thrush calls – a good 95% or more – can be
safely classified as Gray-cheeked Thrushes, due to their overall structure and
the lower frequency nature of the calls. The other 5% or fewer become more
questionable, because of the unknowns between HF Gray-cheeked and LF Bicknell's.
I'd feel pretty safe calling a candidate call a Bicknell's, if it was above
5kHz and had that characteristic abrupt onset (not just humped or arched, as
with classic Gray-cheeked calls), plus that relatively longer wheezy trailing
descent.
Only if we could slap microphones on these birds to record their calls during
their migrations…!
Other insight or comments are very much welcomed in this discussion.
Thanks!
Sincerely,
Chris T-H
PS - I had problems opening Paul's files in Raven as mp3's, so opened in
Audacity and converted to 16-bit WAV files. If desired, I can post them
individually.
On Sep 25, 2013, at 4:02 PM, [email protected] wrote:
Hi Chris,
I'd like to open up a discussion on Bicknell's Thrush calls. There was a
discussion on xeno-canto recently in which there was some questioning of the
validity of the nocturnal calls as there is so much variability and overlap
between Gray-cheeked and Bicknell's daytime calls, more recordings of which are
now available. That not withstanding, I have yet to see a daytime recording of
a known Gray-cheeked that matches the Bicknell's nocturnal call. Isn't it
likely that the Bicknell's call is only one of many different calls Bicknell's
make at night, but perhaps the only one that is definitive? Or perhaps it's a
call that Bicknell's uses more than Gray-cheeked ie there is a quantitative
difference in their calls? There was also a suggestion that perhaps they are
not truly separate species (so perhaps all this is moot).
I recorded several calls last night that match Bicknell's quite well. These are
the first calls I've recorded so far this season that have that appearance, and
were several different birds. All others (100s) going back to September 15th
had been typical lower frequency "buffalo-humped" Gray-cheeked. To me, this
suggests that there is a certain defined population that gives this less common
call.
Paul Driver
Elkins Park PA
-----Original Message-----
From: Christopher T. Tessaglia-Hymes <[email protected]>
To: NFC-L <[email protected]>
Sent: Tue, Sep 24, 2013 11:03 am
Subject: [nfc-l] Migration 9/23-9/24 - HF Gray-cheeks
Last night was an enjoyable night. Quite active for Gray-cheeked-type thrushes
(i.e. there were multiple nice HF candidates in there).
The thrush descent was quite extensive, starting around 5:51am and lasting
until about 6:15am. The peak was from about 6:06am to 6:15pm. Bulk of the
vocally actively descending thrushes were Swainson's Thrushes, with a mere
handful of Gray-cheeked Thrushes toward the beginning.
Several warblers and Rose-breasted Grosbeaks were migrating throughout the
night, although I didn't take a close look at the warblers (a few Ovenbirds,
though). A single White-throated Sparrow and a White-crowned Sparrow
(candidate) were noted.
I've attached the best of the HF Gray-cheeked Thrushes to this message. None of
these are perfect for Bicknell's, but interesting non-the-less.
Here in Etna, NY (located about 180 miles, as the Bicknell's flies, to the SW
of Whiteface Mountain in the Adirondack Mountains) we had NE winds to start the
night, calming and then becoming East winds for the remainder of the night.
Are there any listeners or night recordists immediately due South or Southeast
of Bicknell's Thrush breeding ranges? Just curious to know if there are other
really good examples out there to compare with.
Thanks 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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<poss_bick_3.45am_(2).mp3><poss_bick_5.46am_(2.1).mp3><poss_bick_5.50am_(2).mp3><poss_bick_3.45am_elkins_park_pa_09252013.png><poss_bick_5.46am_elkins_park_pa_09252013.png><poss_bick_5.50am_elkins_park_pa_09252013.png><poss_bick_4.44am_(2).mp3><poss_bick_4.44am_elkins_park_pa_09252013.png>
--
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 List Info:
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Subscribe, Configuration and Leave
Archives:
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BirdingOnThe.Net
Please submit your observations to eBird!
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