An inconspicuous species, the Northern Goshawk is not well monitored by any single survey in Canada. However, considering results from both the Breeding Bird Survey (BBS) and the Christmas Bird Count (CBC), there is sufficient evidence to determine that there has been little overall change in abundance since 1970. Results from both surveys are on the border between what is considered little overall change (< 25% decrease) versus a moderate decrease (> 25% decrease). BBS results suggest a 21% loss of the Canadian breeding population since 1970. However, much of the species' breeding range is north of the area covered by the BBS, and estimated trends within Canadian regions rely on the species' range-wide trend (i.e., the average trend across the BBS survey area, including in the United States) since there are relatively few observations of the species in any one Canadian region. The CBC, which monitors the species during the winter, suggests a moderate decrease (-29%) since 1970 but is less standardized than the BBS. It is also unclear what percentage of Canadian birds winter in the CBC count area. All told, the national population is best described as showing little overall change since 1970, with a slightly negative trend. CBC and BBS results for North America both suggest little overall change in the continental population. This assessment is considered to have medium reliability because both surveys suffer from incomplete coverage of the species' range but provide similar national trend estimates. Because the Northern Goshawk was persecuted in the early part of the 20th century and 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 declined slightly since then, the species, which includes all subspecies except the laingi subspecies, is considered to be below the lowest acceptable level relative to its national population goal (see Canada graph below).
Population trend information specific to the laingi subspecies is not available, but it is assumed that its population has decreased in abundance based on the loss and degradation of its mature forest habitat (COSEWIC 2013a). The subspecies' population goal was set based on the number of home ranges required to support a resilient and well-distributed population (at least 441 home ranges distributed across four regions; Parks Canada Agency 2017). The laingi subspecies is considered to be below the lowest acceptable level relative to its national population goal.
Additional information on: Breeding Bird Survey (BBS) - Canadian analysis
Additional information on: Christmas Bird Count (CBC)
