Following the Grackle Palooza in October, I encountered another blackbird spectacle east of Columbia, Missouri, this morning. On the first winter-like morning of the season, I was driving along a country road when I saw a massive flock of blackbirds in the distance and assumed they were red-winged blackbirds (abundant, permanent residents in this region).
Once I reached their location, however, I found that they were medium-sized blackbirds with yellow eyes, a bluish head and features typical of Brewer's blackbirds. Unlike rusty blackbirds, they did not have plumage markings typical of autumn males and their size, beaks and tails indicated that they were not common grackles. Despite my initial impression, none bore the wing markings of red-winged blackbirds.
I estimated that the flock contained about 2500 individuals and, though various blackbird species often congregate in large, mixed flocks during the colder months, this flock was uniform in its composition. While Brewer's blackbirds were originally a western species, their range has expanded eastward in recent decades. In this particular case, I suspect a potent cold front that pushed across the Midwest in the past 24 hours likely triggered a sudden, mass migration, leading to this morning's spectacle.
Addendum (11/13/22): A day later (this morning), the flock was about two miles south of the original observation site.
