Knocking in San Diego County, California

We went camping for a couple nights near Julian, CA. in a location just a couple miles south of town adjacent to Hwy 79. We arrived on a Friday night and stayed thru Sunday afternoon. We were sharing a tent trailer with friends. Both mornings before dawn I walked my wife over to the nearby porta-potty/restroom. Both nights were clear and quite dark with partial moonlight but the area has a lot of trees so there are shadows even though you can see well enough to walk over to the restrooms without a flashlight. The first morning we walked over to the bathroom without incident and it's very quiet there, especially in the evenings. The second morning probably about 0540 as I waited for my wife I very clearly heard a tree knock. It came from north of our location. When my wife came out of the restroom I told her what I heard and asked her if she heard it. She did not. We walked back to the tent trailer and got back in bed as the sun was not rising until closer to 0700. We were both awake about 15 minutes later and both heard a single whoop sound this time from a bit to the east. Right after the whoop sound was heard there were blue jays in the trees around us that went nuts making all kinds of noise for about 20 seconds then all was quiet again. A bit later, still before dark, I got up and kindled the fire a bit outside and decided to take my vehicle up the road to drop some trash off near the campground office. Another friend from a second tent trailer also camping with us was up at this time. I told her about the tree knock and whoop that was heard. When I returned from the quick errand to the trash bin. She told me she had also heard a tree knock, but this time it was to our west. A few minutes later I heard 2 more whoops one from the south east then a couple minutes after that to the south. These were not coyotes yipping. Not sure what else to say about it but it was interesting!