The house sparrow (Passer domesticus) is a bird of the sparrow family Passeridae, found in most parts of the world. A small bird, it has a typical length of 16 centimetres (6.3 inches) and a mass of 24–39.5 grams (0.85–1.39 ounces). Females and young birds are coloured pale brown and grey, and males have brighter black, white, and brown markings. One of about 25 species in the genus Passer, the house sparrow is native to most of Europe, the Mediterranean region, and much of Asia. Its intentional or accidental introductions to many regions, including parts of Australia, Africa, and the Americas, make it the most widely distributed wild bird.
The house sparrow is strongly associated with human habitations, and can live in urban or rural settings. Though found in widely varied habitats and climates, it typically avoids extensive woodlands, grasslands, and deserts away from human development. It feeds mostly on the seeds of grains and weeds, but it is an opportunistic eater and commonly eats insects and many other foods. Its predators include domestic cats, hawks, owls, and many other predatory birds and mammals.
Because of its numbers, ubiquity and association with human settlements, the house sparrow is culturally prominent. It is extensively, and usually unsuccessfully, persecuted as an agricultural pest, but it has also often been kept as a pet as well as being a food item and a symbol of lust and sexual potency, as well as of commonness and vulgarity. Though it is widespread and abundant, its numbers have declined in some areas. The animal's conservation status is listed as least concern on the IUCN Red List.
The house sparrow is typically about 16 cm (6.3 in) long, ranging from 14 to 18 cm (5.5 to 7.1 in). It is a compact bird with a full chest and a large rounded head. Its bill is stout and conical with a culmen length of 1.1–1.5 cm (0.43–0.59 in), strongly built as an adaptation for eating seeds. Its tail is short, at 5.2–6.5 cm (2.0–2.6 in) long. The wing chord is 6.7–8.9 cm (2.6–3.5 in), and the tarsus is 1.6–2.5 cm (0.63–0.98 in). In mass, the house sparrow ranges from 24 to 39.5 g (0.85 to 1.39 oz). Females usually are slightly smaller than males. The median mass on the European continent for both sexes is about 30 g (1.1 oz), and in more southerly subspecies is around 26 g (0.92 oz). Younger birds are smaller, males are larger during the winter, and females are larger during the breeding season. Birds at higher latitudes, colder climates, and sometimes higher altitudes are larger (under Bergmann's rule), both between and within subspecies.
The plumage of the house sparrow is mostly different shades of grey and brown. The sexes exhibit strong dimorphism: the female is mostly buffish above and below, while the male has boldly coloured head markings, a reddish back, and grey underparts. The male has a dark grey crown from the top of its bill to its back, and chestnut brown flanking its crown on the sides of its head. It has black around its bill, on its throat, and on the spaces between its bill and eyes (lores). It has a small white stripe between the lores and crown and small white spots immediately behind the eyes (postoculars), with black patches below and above them. The underparts are pale grey or white, as are the cheeks, ear coverts, and stripes at the base of the head. The upper back and mantle are a warm brown, with broad black streaks, while the lower back, rump and uppertail coverts are greyish-brown.
The male is duller in fresh non-breeding plumage, with whitish tips on many feathers. Wear and preening expose many of the bright brown and black markings, including most of the black throat and chest patch, called the "bib" or "badge". The badge is variable in width and general size, and some scientists have suggested that patches signal social status or fitness. This hypothesis has led to a "veritable 'cottage industry'" of studies, which have only conclusively shown that patches increase in size with age. The male's bill is black in the breeding season and horn (dark grey) during the rest of the year.
The female has no black markings or grey crown. Its upperparts and head are brown with darker streaks around the mantle and a distinct pale supercilium. Its underparts are pale grey-brown. The female's bill is brownish-grey and becomes darker in breeding plumage approaching the black of the male's bill.
Juveniles are similar to the adult female but deeper brown below and paler above, with paler and less defined supercilia. Juveniles have broader buff feather edges, and tend to have looser, scruffier plumage, like moulting adults. Juvenile males tend to have darker throats and white postoculars like adult males, while juvenile female tend to have white throats. However, juveniles cannot be reliably sexed by plumage: some juvenile males lack any markings of the adult male, and some juvenile females have male features. The bills of young birds are light yellow to straw, paler than the female's bill. Immature males have paler versions of the adult male's markings, which can be very indistinct in fresh plumage. By their first breeding season, young birds generally are indistinguishable from other adults, though they may still be paler during their first year.