The Northern Harrier has a broad breeding distribution in Canada. About half of its breeding population is covered by the Breeding Bird Survey (BBS), despite lower availability of its preferred habitat along BBS routes (e.g., upland graminoid, marsh wetlands). BBS results for Canada indicate that the population has decreased by about 47% since 1970. Trends from most Bird Conservation Regions (BCRs) that host the species show moderate or large decreases, except the Atlantic Northern Forest BCR, which shows little overall change (results for all BCRs with reasonably reliable results are displayed below). Crewe et al. 2016 estimated trends during migration at Hawk Watch sites across the United States and a few sites in eastern Canada. Their results suggest that numbers of Northern Harrier during migration have declined over much of the United States, particularly in the northeast, over the short-term (2005-2016). However, it is difficult to determine how these results reflect on the status of Northern Harrier populations in Canada; the proportion of Canadian breeders migrating through these sites is unknown. Results from the BBS from throughout North America also indicate a decrease in the continental population of Northern Harrier. Because the Northern Harrier was affected by DDT (Farmer et al. 2008), resulting in low levels of abundance at the start of monitoring efforts, and its historical abundance remains unknown, a specific management goal relative to 1970 has not yet been set. However, because the population has continued to decline, it is clear that the species' abundance is below the lowest acceptable level relative to its national population goal (see Canada graph below).
Additional information on: British Columbia Coastal Waterbird Survey
Additional information on: Breeding Bird Survey (BBS) - Canadian analysis
