The bird may stay there until almost light, happens frequently.
I'm off to Brandon tomorrow to band the chicks there today and while I don't think the Radisson chicks are quite ready to fledge, if you see one fly off the ledge, post the time and the details here on the Forum. Pam and Mother Hen will be watching over the chicks and the Forum in my absence - they also have contact numbers in case they are needed. Just so you know, I will be their first phone call.
If you just can't see all the chicks, see what else has been posted, it may be that they chicks are just sleeping and hard to see. Chances are someone will be watching the cam if one fledges today, so READ ALL THE POSTS BEFORE YOU PANIC!
I think we have a couple more days yet, so enjoy the chicks while they are still visible folks ...