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House Sparrows have a mainly vegetarian diet, feeding especially on weed and grass seeds or waste grain, but also on buds, berries, and a range of scraps from humans. During the summer, animal material can account for as much as 10% of the diet and, as opportunists, House Sparrows may take small frogs. mollusks, and crustaceans where available. Nestlings are fed mainly insects for the first few days after hatching .
House Sparrows generally occur in flocks, often quite large ones outside the breeding season. Breeding is mainly in loose colonies of 10 to 20 pairs. Nest building is initiated by an unmated male, but assisted by his mate after pair formation. Nests are typically built in artificial or natural cavities or crevices. These birds are remarkably catholic in their choice of a nest site, with nests reported from moving machinery and even from 640 m below ground in a coal mine in England. Clutch size is typically 3 to 6 eggs. Incubation (for 10 to 14 days) is by both parents. Both parents also feed the nestlings, which leave the nest around two weeks after hatching. Two or three clutches are typically produced each year.
House Sparrows are non-migratory over most of their native and introduced range. This species is among the more abundant birds in the world: the total European population in the 1980s and 1990s probably exceeded 50,000,000 breeding pairs, with an estimated world total of around 500,000,000 pairs. However, significant population declines have been reported in recent years over parts of the native and introduced range (although range expansion elsewhere has continued).
(Kaufman 1996; Summers-Smith 2009 and references therein)