This June has been very interesting, with regard to Black-billed Cuckoo (and,
to a lesser degree, Yellow-billed Cuckoo) movement and vocal activity during
night migration over Etna, NY.
I continue to record calls from different individuals at higher rates compared
to June of last year. According to papers published by Walter Koenig, cuckoo
abundance increases on the year of 13- and 17-year Magicicada emergences, based
upon analysis of BBS data. There is no longer emergence of the Magicicada
broods in our immediate area (I believe these went extinct); however, there has
been abundant emergences to our South and East (110 miles away and 132 miles
away, respectively). If cuckoos have a tendency to wander actively in search of
cicada emergences or caterpillar outbreaks (Malacosoma or Lymantria larvae) –
which could be advantageous to both adult and nestling cuckoos – it would make
sense that cuckoos are significantly more abundant as night migrants this June
because of the relatively nearby emergence of the 17-year cicadas.
Here is an updated link to the call counts for 2013 as well as the link for
last year's call count data:
2013: http://www.northeastbirding.com/Cuckoo/2013Cuckoo.jpg
2012: http://www.northeastbirding.com/Cuckoo/2012Cuckoo.jpg
There have been some proposals that these night vocalizations (grand majority
being "gurgle" night flight calls) could be coming from local birds calling
from immediately nearby locales or while perched in trees.
This is an interesting thought, but seems unlikely for several reasons:
1) Most calls are often individually different from one another (frequency and
cadence differences; also, two different birds have even been heard calling
simultaneously on a few occasions)
2) Birds are sometimes heard clearly producing a sequence of 2-3 calls in
passage (doppler shift)
3) If this many different birds were present locally, one would expect fairly
high numbers being reported in eBird or commonly reported as sightings, posted
on the local birding eList.
Attached are some examples showing just how audibly different these birds have
been. Spectrographically, the calls are measurably different as well.
Thanks for any comments!
Sincerely,
Chris T-H
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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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2013BBCuckooVariability.wav
Description: 2013BBCuckooVariability.wav