There are a lot fewer pigeons in Brandon than there are in Winnipeg, which may be why Alice and Zeus hung out for so long in Winnipeg before heading out to Brandon in 2011. It might be the same thing this year, need to have a definite thaw - for those who aren't in Manitoba we are 10 degrees colder right now than the norm for this date. If they don't have eggs in the box until late April or early May, it won't influence the survival rate of their offspring this year - our birds typically have plenty of time for their young to fledge and become independent before winter sets in.
Still annoying for everyone out in Brandon who wants to be watching peregrines I know ...