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/nfc-l@cornell.edu/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 < c...@cornell.edu> 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, pjd...@aol.com 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 <c...@cornell.edu> > To: NFC-L <nf...@list.cornell.edu> > 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 > -- > *NFC-L List Info:* > Welcome and Basics <http://www.northeastbirding.com/NFC_WELCOME> > Rules and Information <http://www.northeastbirding.com/NFC_RULES> > Subscribe, Configuration and > Leave<http://www.northeastbirding.com/NFC-L_SubscribeConfigurationLeave.htm> > *Archives:* > The Mail Archive<http://www.mail-archive.com/nfc-l@cornell.edu/maillist.html> > Surfbirds <http://www.surfbirds.com/birdingmail/Group/NFC-L> > BirdingOnThe.Net <http://birdingonthe.net/mailinglists/NFCL.html> > *Please submit your observations to eBird<http://ebird.org/content/ebird/> > !* > -- > <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 > > -- > *NFC-L List Info:* > Welcome and Basics <http://www.northeastbirding.com/NFC_WELCOME> > Rules and Information <http://www.northeastbirding.com/NFC_RULES> > Subscribe, Configuration and > Leave<http://www.northeastbirding.com/NFC-L_SubscribeConfigurationLeave.htm> > *Archives:* > The Mail Archive<http://www.mail-archive.com/nfc-l@cornell.edu/maillist.html> > Surfbirds <http://www.surfbirds.com/birdingmail/Group/NFC-L> > BirdingOnThe.Net <http://birdingonthe.net/mailinglists/NFCL.html> > *Please submit your observations to eBird<http://ebird.org/content/ebird/> > !* > -- > -- NFC-L List Info: http://www.NortheastBirding.com/NFC_WELCOME http://www.NortheastBirding.com/NFC_RULES http://www.NortheastBirding.com/NFC-L_SubscribeConfigurationLeave.htm ARCHIVES: 1) http://www.mail-archive.com/nfc-l@cornell.edu/maillist.html 2) http://www.surfbirds.com/birdingmail/Group/NFC-L 3) http://birdingonthe.net/mailinglists/NFCL.html Please submit your observations to eBird: http://ebird.org/content/ebird/ --
