Despite the species' nocturnal habits, the best source of national population change information for the Great Horned Owl comes from the Breeding Bird Survey (BBS). BBS results suggest that the Canadian population has shown a decrease of about 40% since 1970. The extent of this decrease varies across Bird Conservation Regions (BCRs; results for all BCRs with reasonably reliable results are displayed below), but all BCRs except the Prairie Potholes are showing negative trends. Because the BBS covers less than half of the species' breeding population and the estimated trends within Canadian regions rely partly on the species' range-wide trend (i.e., the average trend across the BBS survey area, including the United States) since there are relatively few observations of the species in any one region, we also examined results from the Christmas Bird Count (CBC). Results from the CBC in Canada also indicate a moderate decrease (~45%) in the national population of the Great Horned Owl. Interestingly, both the BBS and CBC show shallower declines at the continental level. Because both surveys agree on the trajectory of the national population, the reliability of this assessment is considered to be high. The Great Horned Owl has been below the lowest acceptable level relative to its national population goal since the early 1990s (see BBS Canada graph below). Future assessments of this species may benefit from regional Nocturnal Owl Surveys, once they amass a longer time series.
Additional information on: Breeding Bird Survey (BBS) - Canadian analysis
Additional information on: Christmas Bird Count (CBC)
