Friday, May 29, 2009

Crow sonograms

Well, I think this may be a retro wave of the future. The sonograms in the Golden guide were considered pretty cutting edge technology when published probably 40 years ago. I never had a lot of success interpreting them, and all successive authors to my knowledge, have omitted them. The widespread use of digital cameras in some ways took identification of rarities back to the "shotgun age" of ornithology where precise scapular patterns, etc can now be easily examined with the bird frozen in time. Well, almost all of those digital cameras have video buttons and perhaps sonogram use will allow "feather-by-feather" or should we say "frequency-by-frequency" dissection of vocalizations. If I'd thought to record the possible worm-eating a few weeks ago I probably would have had a definitive answer and saved an hour of scouting time. At any rate, my old Golden guide has been promoted from the barely-reachable top shelf down to the identification reference shelf, not a place I thought it was ever going to go.

Anyway, an old Washtenaw mentor, Lathe Claflin emailed me some of his crow recordings made along Forest Lawn Rd (with a good old fashioned tape recorder). Here's the sonogram (using free Cornell RavenLite software) from one of the American Crows on his recording calling caw-caw-caw-caw (I think there's a chipping sparrow at the very beginning).

Here's another one, maybe of the same bird (there's a yellowthroat starting witchety-witchety where the harmonics over the 3rd and 4th caw, caw would be).

The American Crow's caw shows as a fairly symmetric arc on the sonogram centered in the 1.5 kHz range with harmonics at about 2.25 kHz, 3.25 kHz, and 5 kHz. The lower registers compare very well with the American Crow sonogram on page 212 of my Golden Guide.

In contrast, here's 3 calls Lathe recorded from the Fish Crow, the caa note.

This one is again in the 1.5-2 kHz range between the reeeeeeeeee of a red-winged blackbird's konklareeeeee (2.5-3 kHz plus harmonics) and the blackbird's call (the L at the end).

The Fish Crow's caa note is a little less symmetric. It is arced, but the body of the call consists of closely parallel arcs in the 1.5 - 2 kHz range which seem to slur down somewhat. Caleb Putnam obtained similar sonograms with his recordings of the caa note, as discussed on his blog here. The Golden guide doesn't have a Fish Crow caa note.

Finally, here's the ca-ha call from my video which you can hear in the fish crow post from earlier this month. The ca is composed of 2 short arcs similar to the caa note, though more symmetric, followed by the more pulsed ha note. This compares very favorably with the ca-ha sonogram in the Golden guide. The ca-ha is the call (song?) is supposed to be very specific for Fish Crow and not made by Americans.

1 comment:

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