These graceful little birds may have been named for their affinity for the old wooden barns once found on many farms, which they could enter and leave with ease through open doors, chinks in the walls and so on.

During autumn migration, Barn Swallows are sociable and often gather in very large flocks (thousands of individuals) of different species. During spring migration, they arrive in Canada in much smaller groups.

Because nearly all of their food (insects) is captured on the wing, Barn Swallows spend a great deal of their time in the air.

The male and the female build their nest together. This activity sometimes takes the two birds eight 14-hour days to complete. The nests are usually constructed of mud mixed with straw, grasses, or horsehair. The nests are cemented to horizontal surfaces, often inside buildings, such as on beams and under overhanging roofs.

Barn Swallows generally have a total length of 15 to 20 cm (6 to 8 in.). Their wings are each about 12 cm (5 in.) long. Females are slightly smaller than males.