The Canadian population of Brewer's Blackbird is monitored best by the Breeding Bird Survey (BBS), which samples most of the breeding range, is well-suited to detecting the species, and has high precision. The national trend shows a steady decline beginning in the early 1980s, amounting to a cumulative loss of 63% of the population. The declines have been somewhat more moderate in the Prairies (the core of the Canadian population) and southern Ontario (the eastern limit of the Canadian range), but particularly severe along the Pacific Coast. Although the continental Christmas Bird Count (CBC) results are heavily influenced by the 71% of the population breeding in the United States, the long-term trend is notably similar, showing a 76% loss since 1970.

The goal for Brewer's Blackbird is to increase the population to the level it was at in the early 1970s, based on the Breeding Bird Survey. Trend data show that Brewer's Blackbird is currently below its goal range and continuing to decline. Analysis considering the historical population loss and recent trend suggests that it is unlikely that the goal can be met by 2050, so the interim target is to reach 60% of the goal by 2050. Achieving this target, and ultimately reaching the national goal for this species, will require deliberate conservation action.