Great Grey Owls Spotted in Southern Ontario

About every 10-20 years, the vole populations in northern Ontario crash causing these beautiful, huge owls to move farther south in search of food.  This winter is the first time that I've been able to see them in the wild.  I counted 4 of them along a one kilometre stretch of road on Monday morning (the owls I have photographed are these ones).   There has been a pair of these owls spotted many times in a field near my house in the city of Barrie.  I haven't had any luck yet finding them.