Throughout its Holarctic breeding range, the Bank Swallow (Riparia riparia) is generally regarded as a riparian species, although it has not been shown to be dependent on riparian vegetation. It is a colonial bird that nests in earthen banks and bluffs, as well as in sand and gravel pits.
Once locally abundant in lowland California (Grinnell and Miller 1944), the Bank Swallow has declined in numbers in recent years and no longer breeds in much of its former range (Remsen 1978). The Bank Swallow has a rather localized distribution in California along rivers, lakes, and ocean coasts (Grinnell and Miller 1944). We estimate that approximately 70–80% of California's remaining Bank Swallows nest along the Sacramento River.