Both the Breeding Bird Survey (BBS) and the Christmas Bird Count (CBC) provide medium reliability estimates of the Canadian population status for Northern Mockingbird. The BBS has a more standardized design, but for this species likely samples a smaller proportion of the population, as numbers appear to be densest in urban areas that are largely not covered by the BBS, and the CBC is therefore considered slightly more reliable. 

Whereas the CBC shows a relatively steady decline amounting to a moderate decrease of 28%, the national BBS trend indicates an increase from the early 1970s to 1990s, followed by a decline back to almost exactly the same level as in the early 1970s. The Atlas of the Breeding Birds of Ontario shows that the number of squares with breeding evidence for the species doubled between the two Atlas periods in the early 1980s and early 2000s (Smith and Poon, 2007). The second Maritimes Breeding Bird Atlas showed that Northern Mockingbird was present in fewer squares than during the first atlas (Horn, 2015), while there was little change in occurrence noted between the two Quebec Breeding Bird Atlases (Atlas of the Breeding Birds of Quebec, 2017). Overall, the data suggest a moderate decrease is most likely, but with only medium confidence, suggesting that little change is also possible.

The goal for Northern Mockingbird is to increase the population to the level it was at in the early 1970s, based on the Christmas Bird Count. Trend data show that Northern Mockingbird is currently below its goal range and continuing to decline. Despite this, analysis of recent trends and potential growth rates suggests that Northern Mockingbird could reach its population goal by 2050, but only if timely conservation action is taken.