A mystery for all my naturalist buddies out there…

I spent the weekend in the swamps of Lousiana, specifically a mixed cypress & palmetto bayou. (Early May, in case this post sticks around for awhile.) We were birding in the middle of the day, and at one point, we stopped because some Gray Gnatcatchers were bopping around in a tree with what may have been a Nashville Warbler.

All of a sudden, a sound started up off to one side. It was not a bird call that anyone recognized (and I was with two people who bird very well by ear.) It was not a gator grunt, nor a green frog banjo-twang, nor any of the tree frogs that I know, nor the buzz of a cicada. It sounded like someone driving with a squeaky fan belt.

“Fan belt bird,” said one of my birding companions.

And then the noise came very much closer and all of a sudden there were several of them calling, all around us, from high off the ground. The noise of multiple…whatevers…calling in this rising-and-falling sound had an incredibly loud, incredibly eerie effect. “It’s aliens,” I said. “Soon the probes will come.”

I have no idea what it actually was. My only guess is some kind of insect, but it could be some kind of frog. Does anybody have any thoughts?