Hi Humblemonk
Sorry no one responded to your post it got buried amongst the other threads and a belated welcome to BF btw.
If you are still checking in, although probably after the fact now, but raptors frequently rest on one leg. Birds also do this to keep warm (a lot of body heat escapes from legs and feet), maybe there was a chill to the wind on the moors that day? There maybe other reasons birds of prey frequently tuck up their talons, Iām not sure where the research stands but who knows, maybe the heat stops the onset of arthritis or other conditions of the feet raptors might be prone to, they can certainly get arthritis in the wings from sprains and injuries.