I have been at a goshawk nest site before, and at the time it seemed apparent that one bird would make itself loud and obvious while the other came silently at the back of your head. These guys will hit hard and draw blood.
Goshawks are nowhere common because they have large territories, so you won't find many in one spot. The nests are hard to find, usually, although when you do they raise a ruckus and you know you're at one.
Check out where they were found during the atlas:
http://www.birdsontario.org/atlas/maps.jsp?lang=en (go there and select northern goshawk from drop-down list)
The blank spaces in between squares with sightings are more likely due to lack of detection than lack of habitat in many cases.
Hopefully I won't draw flak for this, but I would like to suggest that you NOT disclose the nest location in order to allow the birds to nest successfully without human intrusion. These birds give a dramatic reaction to humans near the nest, IMHO there simply is no way to observe or photograph them near the nest without significant disturbance. But you could give us a general area so we can assess the rarity - such as what city or township it is in.
