Yes, it's a Northern/Marsh Harrier
Well, yes and no. The Marsh Harrier is a completely different species they get over the pond. We only get Northern Harriers in Ontario.
Anyway, the brown eyes seen in the photos likely indicate an immature bird, I believe. Also, females tend to have slightly darker eyes than the males.
Also, eye colour shouldn't be used as the mark to compare with a Red-tailed Hawk. Immature red-tails have yellow eyes; they darken with age.
The best things to look at in these photos are the underwing pattern, the presence of a white rump, and, as Kin Lau mentioned in another thread, the face.
The flight style is typically quite different from that of a Red-tailed hawk, as well. You'll be able to tell these guys apart from a distance with a little practice.
More photos, please!