Report 13964: Possible vocalizations heard at sundown near the North Rim of the Grand Canyon

I'm not sure if this is what you are looking for but it is the only thing that strikes my memory when I think back about things I've heard while in the woods. After listening to the sounds you have listed on your site I realized the ones I heard were very similar. I was 15 and my family and I were on a hunting trip in the north Kaibab region of Az. We were there for 4 nights and 5 days. At the end of each day just as the sun was behind the ridge but not quite down we started hearing a high pitched whoop sound. The sound came as a double whoop(whoop,whoop). It was a little higher pitched and shorter. It could be heard from the ridge just west of our campsite about a 1/2 mile or so away. The sound continued for about 2-3 hours or until just after dark. It also sounded as if it was moving around on the ridge and maybe even coming closer as it got louder several times. there was about 30-40 seconds in between each set of whoops. On the second night the sounds started again just like clock work from the same area on the ridge but this time they were answered by another on the ridge just to our southeast. the second sound was alot closer and it would return or answer the one from the west about 1-2 seconds after it would sound. this went on the rest of our trip only from dusk to dark each night. On one of the evenings there was a third whoop that answered in from the north but it seemed farther away and only answered every 15-20 minutes. This made me remember how my father had been hunting in this same spot about 4 years prior and told me how his cab over camper was rocked several times in the night. Each of his hunting buddies swears it wasn't them as they were too drunk to get up and were afraid of what my father slept with for protection. I hope this helps some.