Common Feeder Birds: Cardinal, interesting info on their calls

I am always fascinated with bird song and calls and recently there has been a bit of discussion on the IN-bird listserv about cardinal calls. Specifically, on the Stokes CD, there is a strange call at the end of the cardinal track. When I first heard this call, I was very curious about its origins, but had never taken the time to investigate. The call is almost monkey-like, not one would normally associate with a cardinal. The discussion on the listserv once again peaked my interest, so I did a little sleuthing, found Lang Elliott's e-mail and asked the source. Turns out the call is of a group of cardinals during courtship in the Everglades. Here is Lang Elliott's response when I asked him if he could give some insight on the call. Since I am not super technically savvy, I do not know how to easily add the sound files, but will gladly e-mail them to any interested parties.

Lang Elliott's response:
"I was so very fortunate to get that recording, at the Anhinga Trail parking lot in the Everglades National Park on March 14, 1989, back when I first started recording. It's the only time I've witnessed up close a group of cardinals involved in courtship and competition. Although I cannot say for certain exactly what was going on, nor which sex was making which sound, I can assure you that the sounds were made by cardinals. There were two males and two females in the vicinity. At one point, two if not three birds flew into a thick shrub and began making these sounds. I was very close (hence the immediacy of the recording), although I could not actually see what was going on. Attached is the raw field recording."

"Now, just to prove that cardinals do indeed make the churring sound, attached is an additional recording of a male singing in New York on April 22, 1990. Note the churr that he adds to the end of his song. I have other examples of this, although it is fairly rare and sometimes so soft that people will not notice it. As this recording proves, there's no doubt at all that at least the male cardinal can make such a churring sound (although it's a bit more animated in the courtship sequence)."

So, if anyone wants to hear these sound files, just let me know.