The adult male of Hirundo rustica rustica is 17–19 cm (6.7–7.5 in) long including 2–7 cm (0.79–2.76 in) of elongated outer tail feathers. It has a wingspan of 32–34.5 cm (12.6–13.6 in) and weighs 16–22 g (0.56–0.78 oz). It has steel blue upperparts and a reddish-brown forehead, chin and throat, which are separated from the off-white underparts by a broad dark blue breast band. The outer tail feathers are elongated, giving the distinctive deeply forked "swallow tail". There is a line of white spots across the outer end of the upper tail. The female is similar in appearance to the male, but the tail streamers are shorter, the blue of the upperparts and breast band is less glossy, and the underparts paler. The juvenile is browner and has a paler reddish-brown face and whiter underparts. It also lacks the long tail streamers of the adult.
Diet:Almost exclusively flying insects, although during adverse weather occasionally collects dead or moribund insects on ground.
Habitat: Breeding habitat for the Hirundo rustica includes open areas (e.g., fields) for foraging, a nest site that includes a vertical or horizontal substrate (often enclosed) with some type of roof or ceiling, and a body of water that provides mud for nest building.