Bank Swallows are smaller than other swallows. They can be identified by a broad dark breast-band and white throat, and their constant hard, buzzy, rapid chattering.
Bank Swallows are highly social. They breed in colonies ranging from a few pairs to a couple thousand. They excavate burrows in naturally eroding slopes along streams, rivers, lakes, and oceans. Embankments created by sand and gravel quarries, soil stockpiles, and roadside cuts also provide habitat for colonies. The size and longevity of a colony is dependent on erosion, which maintains suitable nesting habitat. However, the changing nature of banks means Bank Swallow fidelity to breeding sites is low.
Both the male and female excavate the nesting burrow, which is dug 50-90 cm into the bank. The female builds a nest at the burrow's end and lays four or five white eggs, which are incubated for 13-16 days. Nestlings fledge around 18-22 days after hatching, and become independent around 30 days. After the breeding season is completed (early to mid-July), juveniles and adults congregate at daytime staging areas away from the colony along telephone and hydro wires. During migration, roosts are usually located in tall, emergent vegetation in wetlands and marshes.