Made the trip today from Brampton to Bolton. Parked at the side of Humber Station Rd. just north of the Cavalier yard as you suggested and saw a very active group of herons. At one time 3 birds were vying for one nest, it was getting pretty crowded. I reckon I saw 6 herons in total. As a bonus, while looking thro' my bins I heard this wonderful birdsong, I looked up and a bobolink was on the wires directly above me. He stayed a while and then flew over the road to a field on the other side and I watched him for a further 10 mins. Only the second time I've seen one of these, great.