The 10-year migration count trends for Northern Harrier suggest stable or decreasing populations across North America as 56% of sites recorded no statistically significant changes and 43% recorded decreases in counts during this period. The decreasing counts with only one exception were in the East Region (see pie charts and trend maps below). The 20-year count trends (not shown) similarly suggest stable populations except in the East where 13 of 18 trends are decreasing (Central Region: 2 stable; East Region: 7 stable, 19 decrease; Gulf Region: 5 stable; West Region: 5 stable, 1 increase). Both the 10-year and 20-year trends are decreasing at Cape May, New Jersey, the site with the highest counts of Northern Harrier.

Conversely, winter survey data from the Christmas Bird Count (CBC) show mostly stable 10-year trends continent-wide and in the Eastern Region, as 46 of 64 states and provinces, including 23 of 30 in the Eastern Region, show no statistically significant changes. The Northern Harrier is listed as Threatened or Endangered in New England and is a species of conservation concern in Pennsylvania, Oregon, The Great Plains, Southwest, and the Intermountain West primarily due to loss of grassland habitat. It is listed as a species of Least Concern by the IUCN Red List. More research is needed to understand the observed declines in migration counts in the East.