Howdy fellas.
I've long pondered this question but as of yet have not come to any conclusion. Over the years when out deer hunting and such I've occasionally been surprised by loud whooping sounds. IIRC I've usually heard these early in the morning right as the sun is coming up. This call tends to be rather loud and are usually two whoops in succession. I'm pretty sure it isn't an owl, and it certainly isn't a coyote.
The last time I heard this was about a week ago, I was set up in a pop up blind on the edge of the woods over looking a cut bean field. The back of the blind was up tight to a cedar thicket and I had a good view in the other 3 directions. The sun was just starting to peek over the horizon and it was pretty darned cold out. Anyway, as I sat there waiting for the woods to wake up I heard two loud whoops behind me, they came from either the cedar thicket, or from the other side of it.
I find this intriguing because after all the time I've spent in the field over the years I still can't place what would make this call. Any thoughts?