House sparrow

Appearance

The house sparrow can be confused with a number of other seed-eating birds, especially its relatives in the genus "Passer". Many of these relatives are smaller, with an appearance that is neater or "cuter", as with the Dead Sea sparrow.

The dull-coloured female can often not be distinguished from other females, and is nearly identical to the those of the Spanish and Italian sparrows. The Eurasian tree sparrow is smaller and more slender with a chestnut crown and a black patch on each cheek. The male Spanish sparrow and Italian sparrow are distinguished by their chestnut crowns. The Sind sparrow is very similar but smaller, with less black on the male's throat and a distinct pale supercilium on the female.

Naming

The house sparrow was among the first animals to be given a scientific name in the modern system of biological classification, since it was described by Carl Linnaeus, in the 1758 10th edition of "Systema Naturae". It was described from a type specimen collected in Sweden, with the name "Fringilla domestica". Later the genus name "Fringilla" came to be used only for the common chaffinch and its relatives, and the house sparrow has usually been placed in the genus "Passer" created by French zoologist Mathurin Jacques Brisson in 1760.

Distribution

The house sparrow originated in the Middle East and spread, along with agriculture, to most of Eurasia and parts of North Africa. Since the mid-nineteenth century, it has reached most of the world, chiefly due to deliberate introductions, but also through natural and shipborne dispersal.

Its introduced range encompasses most of North America, Central America, southern South America, southern Africa, part of West Africa, Australia, New Zealand, and islands throughout the world. It has greatly extended its range in northern Eurasia since the 1850s, and continues to do so, as was shown by the colonisations around 1990 of Iceland and Rishiri Island, Japan.

The extent of its range makes it the most widely distributed wild bird on the planet.

Status

The house sparrow has an extremely large range and population, and is not seriously threatened by human activities, so it is assessed as Least Concern for conservation on the IUCN Red List.

Behavior

The house sparrow is a very social bird. It is gregarious at all seasons when feeding, often forming flocks with other types of bird. It roosts communally, and its nests are usually grouped together in clumps, and it engages in social activities such as dust and water bathing, and "social singing", in which birds call together in bushes.

The house sparrow feeds mostly on the ground, but it flocks in trees and bushes. At feeding stations and nests, female house sparrows are dominant despite their smaller size, and in reproductive period, being dominant, they can fight for males.

Habitat

It tolerates a variety of climates, but prefers drier conditions, especially in moist tropical climates. It has several adaptations to dry areas, including a high salt tolerance and an ability to survive without water by ingesting berries. In most of eastern Asia the house sparrow is entirely absent, replaced by the Eurasian tree sparrow.

Where these two species overlap, the house sparrow is usually more common than the Eurasian tree sparrow, but one species may replace the other in a manner that ornithologist Maud Doria Haviland described as "random, or even capricious". In most of its range the house sparrow is extremely common, despite some declines, but in marginal habitats such as rainforest or mountain ranges, its distribution can be spotty.

Reproduction

House sparrows can breed in the breeding season immediately following their hatching, and sometimes attempt to do so. Some birds breeding for the first time in tropical areas are only a few months old and still have juvenile plumage. Birds breeding for the first time are rarely successful in raising young, and reproductive success increases with age, as older birds breed earlier in the breeding season, and fledge more young.

As the breeding season approaches, hormone releases trigger enormous increases in the size of the sexual organs and changes in day length lead males to start calling by nesting sites. The timing of mating and egg-laying varies geographically, and between specific locations and years. This is because a sufficient supply of insects is needed for egg formation and feeding nestlings.

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.

Males may try to mate with females while calling or displaying. In response, a female will adopt a threatening posture and attack a male before flying away, pursued by the male. The male displays in front of her, attracting other males, who also pursue and display to the female. This group display usually does not immediately result in copulations.

Other males usually do not copulate with the female. Copulation is typically initiated by the female giving a soft "dee-dee-dee" call to the male. Birds of a pair copulate frequently until the female is laying eggs, and the male mounts the female repeatedly each time a pair mates.

The house sparrow is monogamous, and typically mates for life. Birds from pairs often engage in extra-pair copulations, so about 15% of house sparrow fledglings are unrelated to their mother's mate.

Male house sparrows guard their mates carefully to avoid being cuckolded, and most extra-pair copulation occurs away from nest sites. Males may sometimes have multiple mates, and bigamy is mostly limited by aggression between females.

Many birds do not find a nest and a mate, and instead may serve as helpers around the nest for mated pairs, a role which increases the chances of being chosen to replace a lost mate. Lost mates of both sexes can be replaced quickly during the breeding season. The formation of a pair and the bond between the two birds is tied to the holding of a nest site, though paired house sparrows can recognise each other away from the nest.

The eggs are white, bluish-white, or greenish-white, spotted with brown or grey. Subelliptical in shape, they range from 20–22 mm in length and 14–16 mm in width, have an average mass of 2.9 g, and an average surface area of 9.18 cm2.

The female develops a brood patch of bare skin and plays the main part in incubating the eggs. The male helps, but can only cover the eggs rather than truly incubate them. The female spends the night incubating during this period, while the male roosts near the nest. Eggs hatch at the same time, after a short incubation period lasting 11–14 days, and exceptionally for as many as 17 or as few as 9. The length of the incubation period decreases as ambient temperature increases later in the breeding season.

Young house sparrows typically remain in the nest for 11 to 23 days, normally 14 to 16 days. During this time, they are fed by both parents. As newly hatched house sparrows do not have sufficient insulation they are brooded for a few days, or longer in cold conditions. The parents swallow the droppings produced by the hatchlings during the first few days; later, the droppings are moved up to 20 m away from the nest.

The chicks' eyes open after about four days and, at an age of about eight days, the young birds get their first down. If both parents perish, the ensuing intensive begging sounds of the young will often attract replacement parents who feed them until they can sustain themselves. All the young in the nest leave it during the same period of a few hours. At this stage they are normally able to fly. They start feeding themselves partly after one or two days, and sustain themselves completely after 7 to 10 days, 14 at the latest.

Food

As an adult, the house sparrow mostly feeds on the seeds of grains and weeds, but it is opportunistic and adaptable, and eats whatever foods are available. In towns and cities it often scavenges for food in garbage containers and congregates in the outdoors of restaurants and other eating establishments to feed on leftover food and crumbs.

It can perform complex tasks to obtain food, such as opening automatic doors to enter supermarkets, clinging to hotel walls to watch vacationers on their balconies, and nectar robbing kowhai flowers. In common with many other birds, the house sparrow requires grit to digest the harder items in its diet. Grit can be either stone, often grains of masonry, or the shells of eggs or snails; oblong and rough grains are preferred.

Animals form another important part of the house sparrow's diet, chiefly insects, of which beetles, caterpillars, dipteran flies, and aphids are especially important. Various non-insect arthropods are eaten, as are molluscs and crustaceans where available, earthworms, and even vertebrates such as lizards and frogs.

Young house sparrows are fed mostly on insects until about fifteen days after hatching. They are also given small quantities of seeds, spiders, and grit. In most places, grasshoppers and crickets are the most abundant foods of nestlings. True bugs, ants, sawflies, and beetles are also important, but house sparrows will take advantage of whatever foods are abundant to feed their young. House sparrows have been observed stealing prey from other birds, including American Robins.

Migration

Most house sparrows do not move more than a few kilometres during their lifetime. However, there is limited migration in all regions. Some young birds disperse long distances, especially on coasts, and mountain birds move to lower elevations in winter. Two subspecies, "bactrianus" and "parkini", are predominately migratory. Unlike the birds in sedentary populations that migrate, birds of migratory subspecies prepare for migration by putting on weight.

Cultural

To many people across the world, the house sparrow is the most familiar wild animal and, because of its association with humans and familiarity, it is frequently used to represent the common and vulgar, or the lewd. One of the reasons for the introduction of house sparrows throughout the world was their association with the European homeland of many immigrants.