Dear NFCers,
My colleague Manuel Grosselet and I recorded an unidentified night flight call 
in southern Mexico (near Minatitlan) in fall 2012.  We call it “the big 
double-up” for obvious reasons as one can see in the attached spectrograms. We 
recorded 32 of the calls near Minatitlan from Oct 16-Dec 3, 2012.  What 
distinguishes it from other “double-ups” one commonly encounters in eastern US 
is the combination of the call’s broad frequency expanse (~5 kHz on average), 
the relatively large maximum frequency gap between its component tones (~ 2 kHz 
on average), and its much longer overall duration, ~85 mS on average, which is 
roughly twice as long as the Tennessee, Orange-crowned, Nashville , and 
Black-throated Green double-up complex.
Based on my not seeing this call type in 25+ years of spectrographic night 
flight call study across eastern US, I conclude that it is a species that does 
not likely migrate across eastern US.  To support this contention, I’m 
soliciting feedback from the untamed multitude of others monitoring nfcs these 
days as to whether you have encountered this big double-up call type in the 
eastern US, or anywhere in North America.  A short audio clip of the call is 
also attached.   Many thanks,  Bill Evans


NFC-L List Info:


Please submit your observations to eBird:


Attachment: Tseep_2012-10-16_00.42.36_00.wav
Description: Wave audio

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