Only 5 to 51/2 inches long, the northern rough-winged swallow is brown-backed with dirty-white underparts, a short notched tail, and narrow pointed wings. The rough-winged swallow lacks the distinct dark breast band of the bank swallow. Its legs are short, and its feet adapted more for perching than for walking. For such a common species, the northern rough-winged swallow is not well known because it is often overlooked among other swallows.
The rough-winged swallow is not very vocal at any time, but it does utter short, harsh zeep sounds in flight. The small serrations on its outer wing feathers, for which the species is named, produce fluttery noises during courtship displays.
Like all swallows, the rough-winged is a bird of open country. It may be found from sea level to 6,000 feet or more, and it is often (though not always) found near some kind of water. In all except the southernmost parts of the country, these are seasonal birds, arriving in early spring and departing by mid- to late fall.
Its diet consists almost entirely of flying insects that are snatched in midair. Like other birds that catch their prey in flight, rough-winged swallows have wide gaping mouths to maximize their chances for success. Flies, wasps, winged ants, moths, and damselflies are favored items. They drink on the wing, barely breaking the surface of the water in a lake or pond to satisfy their thirst without wetting their wings.
Rough-winged swallows breed in sandbanks or other vertical sites, such as road cuts or soft cliffs. Using their feet, they excavate a deep (up to six feet) burrow. Two or three pairs may nest in proximity, but this species does not breed in large colonies like the bank swallow. The pair constructs a twiggy nest at the end of the burrow. Five to seven eggs are laid, and incubation by the female takes 12 to 16 days. Both parents feed the nestlings, which leave the nest at about 20 days of age.