The Canadian population of Northern Harrier is best monitored by the Breeding Bird Survey (BBS), which samples a high proportion of the Canadian breeding range and has high precision in trend estimates. The national trend has fluctuated somewhat over time, but overall shows a sustained decline from the early 1970s to the present, amounting to a large decrease of 67%. All regions with sufficient data for medium reliability trend estimates show declines, with the greatest occurring in the southern Northwest Territories through the Prairie provinces, and the slightest in British Columbia and the Maritimes. Trends since at least the mid-1990s are also available from six locations through the Raptor Population Index, with moderate increases at two of three sites in Quebec, but slight to moderate declines at all three sites in Ontario.

The goal for Northern Harrier is to increase the population to the level it was at in the early 1970s, based on the Breeding Bird Survey. Trend data show that Northern Harrier is currently below its goal range and continuing to decline. Analysis considering the historical population loss and recent trend suggests that it is unlikely that the goal can be met by 2050, so the interim target is to reach 60% of the goal by 2050. Achieving this target, and ultimately reaching the national goal for this species, will require deliberate conservation action.