In reply to mattck:
I had a look this morning, and I think they have actually nested in this spot. The hole with all the droppings is an ideal nest site, and with bits of down, and lots of pellets and splashing, certainly looks like a used (successful) Kestrel scrape. No chicks present now so presumably fledged but still using the crag.
Once they have settled in a spot (they can be disturbed more easily in the early stages of breeding), Kestrels seem pretty tolerant of people and the females will sit surprisingly tight on the eggs. On the most popular routes there (Bamford Wall etc) people would be out of line of sight of the hole, and there are relatively fewer ascents of Oracle. Also, the floor of the hole extends a long way back into the crag so there would be plenty of space for chicks to retreat/hide from climbers once they got to that stage.
That said, it would be good to hear if anyone did see anything while climbing any of these routes in the last couple of months so we could confirm successful breeding.
Another Kestrel pair nested in the quarry at Bamford and fledged 6 young this year too.