Oh the plot thickens..there was an intruder..that's why mom panicked!! Can't post the link as you have to be registered but someone got photos and here was commentary:
In the last pic is the parent is sitting on pipe, in the next picture is an intruder, a immature Falcon note no black feather patern on chest, smaller, no leg feathers, it is also on the edge of scrape box,
Kit says parent returned to find intruder and may have battled it as in pic later of parent on nest feathers indicate a battle, she thinks the mother was desprate to get chick and eggs protected and chick was unwilling, she was tryiing to protect the chick and ended up over edge of scrap