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
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Tseep_2012-10-16_00.42.36_00.wav
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