Recorded this a minute ago, with my rooftop mic. When I hear these high-pitched sustained alarms it is usually an indication of a raptor visible somewhere. But this particular bird maintained this call for 30-40 seconds. It was doing a submissive/solicitation display, complete with wing fluttering and crouched posture, and none of the local birds were at all concerned about a predator and freely flew to and from the feeder.
Anyone know what species this is? Would you recognize this without looking if you heard it but couldn't see the source?