I DID see him but not until the 4th pic.
BUT - There was a GHO we released at the site of the rehab facility where I worked in Tucson. She would come for mouse treats and had three clutches of eggs at the site. There were times when I would stand under a tree, knowing she was right there but I couldn't see her.
I've had the same thing happen with rattlesnakes. They can smell the trails used by rodents and will curl up and wait there for hours at a time. There was one of those spots outside my kitchen window in AZ and times when I had seen the snake there, knew he was there but had to hunt to find him.
Nice shots of my favorite bird strollingbones. And thanks for the link. I had seen it before but had forgotten about it.