I probably set the gain too high when I was recording. The hum is selfnoise for my recording unit, which is (unfortunately) a video camera. I think it's caused by the motor that drives the tape- with my new tapeless system I think I've reduced this noise quite a bit (for new recordings.) Thanks for the input.
Were they green? If so, they're probably tropical parrots. There's a huge flock that comes by my area every year now, by the hundreds, and they are LOUD... and yes, very annoying. :) The whole flock actually parked right outside my bedroom in the trees this fall and I beat myself up that I didn't have any batteries in my microphone!