House sparrows are small noisy birds found in most parts of the world. Their plumage is mostly different shades of grey and brown. Females and young birds are colored pale brown and grey, and males have brighter black, white, and brown markings. Because of their numbers, ubiquity, and association with human settlements, House sparrows are culturally prominent. They are extensively, and usually unsuccessfully, persecuted as agricultural pests. They have also often been kept as a pet, as well as being a food item.
House sparrows are native to most of Europe, the Mediterranean Basin, a large part of Asia, and parts of North Africa. These birds are strongly associated with human habitation and can live in urban or rural settings. They are found in widely varied habitats and climates but typically avoid extensive woodlands, grasslands, and deserts away from human development. The only terrestrial habitats that House sparrows do not inhabit are dense forest and tundra.
House sparrows are very social birds. They are gregarious during all seasons when feeding, often forming flocks with other species of birds. They roost communally and while breeding nests are usually grouped together in clumps. House sparrows also engage in social activities such as dust or water bathing and "social singing", in which birds call together in bushes. These little birds feed mostly on the ground, but they flock in trees and bushes. At feeding stations and nests, females are dominant despite their smaller size, and they can fight over males in the breeding season. On the ground, House sparrows typically hop rather than walk; they can also swim when forced to do so by pursuit from predators. Most House sparrows do not move more than a few kilometers during their lifetimes. However, limited migration occurs in all regions. Some young birds disperse long distances, especially on coasts, and mountain birds move to lower elevations in winter. House sparrows are highly noisy. Most of their vocalizations are variations of their short chirping call that may sound as 'chirrup', 'tschilp', or 'philip'; this note is made as a contact call by flocking or resting birds, or by males to proclaim nest ownership and invite pairing. Much communal chirping occurs before and after the birds settle in the roost in the evening, as well as before the birds leave the roost in the morning. Aggressive males give a trilled version of their call, transcribed as 'chur-chur-r-r-it-it-it-it'. This call is also used by females in the breeding season, to establish dominance over males while displacing them to feed young or incubate eggs.
House sparrows are omnivores and eat whatever foods are available. They feed mostly on the seeds of grains and weeds, buds, berries, and fruits such as grapes and cherries. They also commonly eat insects, mollusks, and crustaceans where available, earthworms, and even vertebrates such as lizards and frogs.
House sparrows are monogamous and typically mate for life. Many birds do not find a nest and a mate, and instead may serve as helpers around the nest for mated pairs; this role also increases the chances of being chosen to replace a lost mate. Males take up nesting sites before the breeding season, by frequently calling beside them. Unmated males start nest construction and call particularly frequently to attract females. When a female approaches a male during this period, the male displays by moving up and down while drooping and shivering his wings, pushing up his head, raising and spreading his tail, and showing his bib. House sparrows breed in colonies and generally produce 2 broods per year. Their nests are most frequently built in the eaves and other crevices of houses. Holes in cliffs and banks, or tree hollows, are also used. House sparrows sometimes excavate their own nests in sandy banks or rotten branches, but more frequently use the nests of other birds in banks and cliffs, and old tree cavity nests. The female lays 4 or 5 white, bluish-white, or greenish-white eggs, spotted with brown or grey. She develops a brood patch of bare skin and plays the main part in incubating the eggs which lasts 11-14 days. The male helps, but can only cover the eggs rather than truly incubate them. The helpless chicks remain in the nest for 14 to 16 days and during this time, they are fed by both parents. The young can breed in the breeding season immediately following their hatching; however, in tropical areas, some birds start to breed when they are only a few months old and still have juvenile plumage.
The main threats to House sparrows include predation, in particular by Eurasian sparrowhawks, electromagnetic radiation from mobile phones, and diseases such as avian malaria. A primary cause of the decline seems to be an insufficient supply of insect food for nestling sparrows. Declines in insect populations result from an increase of monoculture crops, the heavy use of pesticides, the replacement of native plants in cities with introduced plants and parking areas, and possibly the introduction of unleaded petrol, which produces toxic compounds. House sparrows are also common victims of roadkill, especially in Europe.
According to the IUCN Red List, the global House sparrow population size is 896,000,000-1,310,000,000 mature individuals. The European population consists of 134,000,000-196,000,000 pairs, which equates to 269,000,000-392,000,000 mature individuals. National population sizes include around 100-100,000 breeding pairs in China and around 100-100,000 breeding pairs in Russia. Overall, currently, this species is classified as Least Concern (LC) on the IUCN Red List but its numbers today are decreasing.
House sparrows consume large quantities of seeds and thus have an impact on various plant communities. They also serve as an important food source for birds of prey, domestic cats and dogs, and other predators that occur near human habitations.