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Tuesday, May 26, 2009

Fish Crow recording analysis

I have spent hours trying to manipulate my (what I thought were decent) recordings of the Fish Crow, with little success. The versions in the blog post below are ambient captures of the recordings played through my computer- long story... 

Anyway, to begin to look at these recordings more technically, I used RavenLite to produce sonograms of the single caw note this bird gave repeatedly, and to compare with know
n Fish Crow recordings and calls of American Crows as well. Here are the two recordings posted yesterday. First, the single caw note by itself (the caw is the blob directly below the re
d box):
All of the tones here are in the 1.2-1.8 kHz range, with an obvious downlur and 2 overtones. The duration is about 0.127 seconds.

Here is the second recording, in which several American Crows are calling before and after the caw is heard (again the FICR caw is directly below the red box):

Here, all of the tones are in the 1.2-1.9 kHz range, downslurred, and with 2-3 overtones as well. Duration of the call is about 0.115 seconds. In the field, the "caw" note sounded the same each time I heard it, and it was the only sound the bird produced. I heard it in a series of at least 5 calls on one occasion and at least 3 calls in another. The only time I heard a double call I was unable to record it unfortunately.

For comparison, here is a recording from the MaCaulay Library, recorded 25 May 1980 by Thomas H. Davis in New York state (ML AUDIO 26

I selected this recording because it was a single note (not the caw-aw sound) given repeatedly that sounded similar to what I heard, and not some kind of aberrant or context-specific call given singly. Here the sound occurs in the 1.2-1.8 kHz range, also downslurred and with 2-3 overtones and duration about 0.20 seconds. The harmonic above this call is not visible in my recordings, and is likely due to a much better sound quality of the latter recording. 

Finally, here is an American Crow (ML AUDIO 105346) recorded 7 May 1994 in Maryland b
y Geoffrey A. Keller:

Note the very different shape, duration, and especially the modulation of each tonal stripe which is absent in the Fish Crow calls. The range of frequencies here is 1.0-2.3 kHz (or possibly higher depending on which tones you "count"), with duration 0.47 seconds.

Finally, here is a comparison of the first American Crow (left), the Berrien Co. bird (middle), and the New York Fish Crow (right). I'll let you make your own conclusions:

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