2011 was late for Cowboy and Kate who ultimated didn't have a successful nest and Alice & Zeus were held up for a month, not so much because of the flooding, which hadn't happened by this point but rather that there was snow and prey species were slow to move north. Although Alice ended up in Brandon, she had spent the previous year in Winnipeg and Zeus would know where to find food anywhere in this province after 16 years, and Kate and Cowboy aren't residents, so they found food and weren't moving until more food was on the way.
This year, not so much snow, I would think that end of the month is a pretty good guess - particularly since Jules is back pretty much on her regular schedule, particularly with all the prey species turning up very fast in places like Fort Whyte and Oak Hammock Marsh.
But that's just my impression, we'll have to see what you and Rose and others out in Brandon see when the times come ....