Haven't seen hide nor feather of either Chapelle or Vimy since just after Chapelle fledged ... maybe one of those years when the kids leave home right after fledging ...
Even if the fledglings never return to the nest box, would we not see Princess & Smiley teaching them how to fly & hunt somewhere in the downtown area? Or could they just immediately fly off elsewhere? 
I was wondering that, too. My husband and I went downtown last night as I thought we might see them flying around.
Some years the chicks hang out together in the downtown area, some years they return to the nestbox to hang out, eat and nap, and then some years, they fledge and we don't see them again unless it is as they fly by. Their parents will keep track of them, feed them, encourage them to improve their flight skills and then start teaching them how to hunt and then they are independent and they (the chicks) will leave Winnipeg to go exploring before migrating in the fall. Last year chicks from Manitoba were spread out from Alberta to Ontario and down to North Dakota at the same time. Then they all started to move in unison southwards but they never hooked up again and all overwintered in very different locations (100s of kms between them).
We may see Chapelle & Vimy after they become more confident of their flying skills and start to explore more on their own - no unusual for them to reappear after a month or two at the Radisson for a day, or a week and then they are gone.
As much as we would like to see them again, learning to fly safely without crashing into things is really what we want!
