Big problems with those kent-like calls

Cornell has provided some good "kent call" information here.

In my analysis of the data at the link above, I see a couple of major reasons that these calls were almost certainly not produced by Ivory-bills.

1. First, compare the spectograms.

Here's the spectogram for the January 29, 2005 ARU recording:


Here's the spectogram for an actual 1935 Ivory-bill recording:


The two spectograms just don't match. One big difference is the duration of the individual notes--in the case of the 1935 Ivory-bill, the notes are consistently about .1 second long; in the ARU data, the notes are much longer (more like .2 or .3 seconds in length).

Another large difference is the number of overtones or harmonics shown above the 2khz range in the Ivory-bill recording. These overtones or harmonics account for the far richer quality of the Ivory-bill notes (this is especially apparent if you use a good set of headphones as you listen on your computer). A third difference is the slight downslurring/upslurring ("U" shape) seen in the Ivory-bill notes but not in the ARU notes.

Now, I know that Cornell tried "degrading" the original Ivory-bill calls by broadcasting them through foliage at 145 meters, then re-recording them. If you're interested, you can check out those results here.

I'm not impressed with that approach--it's like trying to match a uselessly fuzzy "bird" photo with a uselessly fuzzy photo of an Ivory-bill model.

2. Here's the other major reason that I believe the ARU calls are not Ivory-bill notes: in both examples, the ARU birds hit some "sour notes" not present in the actual Ivory-bill recording.

Here's a link to the sound and spectograms for the January 31, 2005 kent-like calls. This bird produces two downslurred "sour notes" (at the 11 second and 18 second marks) that sound very much unlike the Ivory-bill's kent notes. The final note (at the 18 second mark) sounds to me like a fairly typical Blue Jay note.

Here's a link to the sound and spectograms for the January 29, 2005 kent-like calls. As in the January 31 example above, this bird hits a downslurred "sour note" (at the 5 second mark).

I've previously written about the ARU kent-like calls here.

I think this note from Cornell's web site is also interesting:

Some observers in Arkansas have been surprised to hear Blue Jays making purely "kent"-like calls for extended periods.