This final note today, which I dunno, this is one of those times where you should listen to the audio by clicking on the Soundcloud player below (or go to this link).
That was in fact turkeys -- 300 of 'em. Recorded in 1973.
Seems there's actual science that shows turkeys can in fact be made to gobble on cue. The guy who did the recording, a reporter for KPFA, a public radio station in Berkeley, Calif., said the trick was to do it without aggravating the birds.
Which apparently... did happen once.