Holes are preferred as nest sites, but nooks and crannies in outbuildings and open sites in trees and shrubbery are also used. The young form flocks soon after fledging, and most disperse from the natal colony. Large postbreeding flocks roost in trees or brush near grain fields in agricultural areas or in cities, from which they fly to feeding areas. After arriving at the congregation site, the birds often engage in communal singing for up to an hour. .

Although House Sparrows belong to a different family of birds, they closely resemble North American sparrows. They are short and stocky with shorter legs and thicker bills than native sparrows. The back is brown with black streaking. The breast and belly are unstreaked dull gray. Males in breeding plumage have a gray crown, with chestnut bordering the crown and extending down the back of the neck. The cheek and side of the neck is white. A black bib extends to the throat and meets the black stripe in front of the eye. The bill is dark gray black, and the legs are pale brown. The rump is gray, the shoulders are chestnut, and the wings are brownish with a white wing bar. The tail is dusky gray brown. Fall and winter males may lack the bright colors and black bib. .

Females have a grayish brown crown and a grayish buff superciliary stripe. They lack the chestnut and black colors of the male, and their upperparts and wings are much grayer than the male. The back is light brown with black streaks; the rest of the head, breast, and sides are grayish brown. The belly is dull white. The bill and legs are pale brown. Immature males resemble females, except for the darker crown and a faint grayish bib.