Both are migratory, wintering in the southern United States and Mexico, although some Brewer's blackbirds are present all year in the western US.
They build cup nests, and the female alone incubates the eggs. They are gregarious outside the breeding season.
Both species feed on seeds and insects, the rusty having a particularly high insect component to its diet. The fortunes of the two species are contrasting, with Brewer's expanding east in the Great Lakes region, while rusty shows a worrying decline in numbers.
References
^"Icteridae". aviansystematics.org. The Trust for Avian Systematics. Retrieved 2023-07-16.