Animalia

The House Sparrow (Passer domesticus) is a species of passerine bird of the sparrow family Passeridae. It occurs naturally in most of Europe, the Mediterranean region, and much of Asia. It has also been intentionally or accidentally introduced to many parts of the world, making it the most widely distributed wild bird. It is strongly associated with human habitations, but it is not the only sparrow species found near houses. It is a small bird, with feathers mostly different shades of brown and grey.

Description

The House Sparrow is a chunky bird,^[2] typically about 16 centimetres (6.3 in) long, ranging from 14–18 centimetres (5.5–7.1 in).^[3] It has a large rounded head, a short tail, and a stout bill.^[2] In weight, the House Sparrow generally ranges from 24–39.5 grams (0.85–1.39 oz).^[4] Weight varies by sex, with females usually smaller than males.^[4] Younger birds are smaller, males are larger during the winter, and females larger during the breeding season.^[5] Between and within subspecies, there is further variation based on latitude, altitude, climate, and other environmental factors, under biological rules such as Bergmann's rule.^[5][6][7][8]

The plumage of the House Sparrow is mostly different shades of grey and brown. The sexes differ, with females and juveniles mostly buff, and the male marked with bold colours.^[7] The male is duller in fresh non-breeding plumage, with buff tips on many feathers. Wear and preening expose bright markings of brown and black, including a throat and chest patch, called a "bib" or a "badge".^[9] This patch is variable in width and general size, and some scientists have suggested that patches signal social status or fitness, a hypothesis which has led to a "veritable 'cottage industry'" of studies, which have only conclusively shown that patches increase in size with age.^[10] In breeding plumage, the male's crown is grey, and it is marked with black on its throat and beneath its crown. The cheeks and underparts are pale grey. The mantle and upper back are a warm brown, broadly streaked with black, while the lower back, rump and uppertail coverts are a greyish-brown.^[11] The female has no black on head or throat, nor a grey crown and its upperparts are streaked with brown.^[12] The juvenile is deeper brown, and the white is replaced by buff; the beak is pink to dull yellow.^[12]

There is some variation in the twelve subspecies of House Sparrow. The subspecies are divided into two groups, the Oriental indicus group, and the Palaearctic domesticus group. Birds of the domesticus group have grey cheeks, while indicus group birds have white cheeks, as well as bright colouration on the crown, a smaller bill, and a longer black bib.^[13] The subspecies Passer domesticus tingitanus differs little from the nominate subspecies, except in the worn breeding plumage of the male, in which the head is speckled with black and underparts are paler.^[14] P. d. balearoibericus is slightly paler than the nominate but darker than P. d. bibilicus.^[15] P. d. bibilicus is paler than most subspecies, but has the grey cheeks of domesticus group birds. The similar P. d. persicus is paler and smaller, and P. d. niloticus is nearly identical but smaller.^[14] Of the less wide ranging indicus group subspecies, P. d. hyrcanus is larger than P. d. indicus, P. d. bactrianus is larger and paler, P. d. parkini is larger and darker with more black on the breast than any other subspecies, and P. d. hufufae is paler.^[14][16][17]

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.^[18] The dull-coloured female often can not be distinguished from other birds, and it is nearly identical to the females of the Spanish Sparrow and Italian Sparrow.^[11] The Eurasian Tree Sparrow is smaller and more slender with a chestnut crown and a black patch on each cheek.^[19] The male Spanish Sparrow and Italian Sparrow are distinguished by their chestnut crowns. The Sind Sparrow is smaller, with the male less black on the throat and the female usually having a distinct pale supercilium.^[11]

Voice

Male calling in San Francisco

All of the House Sparrow's vocalisations are variations on its short and incessant chirping call. Transcribed 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.^[20] In the breeding season this call becomes what is called an "ecstatic call", which is similar to a song, as it is uttered by the male at great speed.^[20] Young birds, especially in captivity, also give a true song, a warbling similar to that of the European Greenfinch.^[21] Aggressive male House Sparrows 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.^[22] The House Sparrow gives a nasal alarm call, the basic sound of which is transcribed as quer, and it gives a shrill "chree" call in great distress.^[23] Another House Sparrow vocalisation is what has been described as an "appeasement call", a soft quee given to inhibit aggression, usually by a mated pair.^[22] These vocalisations are not unique to the House Sparrow, but are shared with small variations by all sparrows.^[24]

Taxonomy

The House Sparrow is part of the sparrow genus Passer, which contains about 20 species, depending on the authority.^[25] Most species in the genus are between 11 and 16 cm (4–6 in) long, dull-coloured birds with short square tails and stubby conical beaks.^[7][26] Mitochondrial DNA suggest that speciation in Passer occurred during the Pleistocene and earlier, while other evidence suggests speciation occurred 25,000 to 15,000 years ago.^[27] Within Passer, the House Sparrow is part of the "Palearctic black-bibbed sparrows" group and a close relative of the Mediterranean "willow sparrows".^[28][29]

The taxonomy of the House Sparrow and its Mediterranean relatives is highly complicated. The common type of "willow sparrow" is the Spanish Sparrow, which resembles the House Sparrow in many respects.^[30] It frequently prefers wetter habitats than the House Sparrow, and it is often colonial and nomadic.^[31] In most of the Mediterranean, one or both species occur, with some degree of hybridisation.^[32] In North Africa, the two species hybridise extensively, forming highly variable mixed populations with a full range of characters from pure House Sparrows to pure Spanish Sparrows and everything between.^[33][34][35]

In much of Italy there is a type of sparrow apparently intermediate between the House and Spanish sparrows, known as the Italian Sparrow. It resembles a hybrid between the two species, and is in other respects intermediate. Its specific status and origin are the subject of much debate.^[34][36] In the Alps, the Italian Sparrow intergrades over a roughly 20 km (12 mi) strip with the House Sparrow,^[37] but to the south it intergrades over the southern half of Italy and some Mediterranean islands with the Spanish Sparrow.^[34] On the Mediterranean islands of Malta, Gozo, Crete, Rhodes, and Karpathos, there are other apparently intermediate birds of unknown status.^[34][38][39]

The bird's usual English and scientific names have the same meaning. The Latin word passer, like the English word "sparrow", is a term for small active birds, coming from a root word referring to speed.^[40][41] The Latin word domesticus means "belonging to the house", like the common name a reference to its association with humans.^[42] The House Sparrow was scientifically described by Carl Linnaeus in the 1758 edition of his Systema Naturae, as Fringilla domestica.^[43] Later the name Fringilla came to be used only for the Chaffinch and its relatives, and House Sparrow as placed in the genus Passer created by French zoologist Mathurin Jacques Brisson in 1760.^[44][45] The House Sparrow is called by a number of other names, including English Sparrow, chiefly in North America;^[46][47] and Indian Sparrow or Indian House Sparrow, for the birds of the Indian subcontinent and Central Asia.^[48] Dialectal names include sparr, sparrer, spadger, spadgick, and philip, mainly in southern England; spug and spuggy, mainly in northern England; spur and sprig, mainly in Scotland;^[49][50] and spatzie or spotsie in North America.^[51]

Subspecies

A male of the subspecies indicus

A large number of subspecies have been named, of which twelve were recognised in the Handbook of the Birds of the World.^[25] These subspecies are divided into two groups, the Palearctic domesticus group, and the Oriental indicus group.^[25] Several Middle Eastern subspecies, including Passer domesticus biblicus, are sometimes considered a third group. The subspecies P. d. indicus was described as a species, and considered one by many ornithologists during the nineteenth century.^[13] Migratory birds of the subspecies P. d. bactrianus in the indicus group were recorded overlapping with the P. d. domesticus without hybridising in the 1970s, so the Soviet scientists Edward I. Gavrilov and M. N. Korelov proposed indicus to be a separate species.^[44][52] This split is rarely recognised, since indicus group and domesticus group birds intergrade in a large part of Iran.^[25]

• domesticus group
  • P. d. domesticus, the nominate subspecies described by Linnaeus from Sweden, is the found in most of Europe, across northern Asia to Sakhalin and Kamchatka. It is the subspecies most widely introduced worldwide.^[53]
  • P. d. balearoibericus, von Jordans, 1923, described from a specimen collected at Majorca, is found in the Balearic Islands, southern France, the Balkans, and Anatolia.^[25]
  • P. d. tingitanus, (Loche, 1867), described from a specimen from Algeria, is found in the Maghreb from Ajdabiya in Libya to Béni Abbès in Algeria, and to Morocco's Atlantic coast. It hybridises extensively with the Spanish Sparrow, especially in the eastern part of its range.^[54]
  • P. d. niloticus, Nicoll and Bonhote, 1909, described from Faiyum, Egypt, is found along the Nile north of Wadi Halfa. It intergrades with bibilicus in the Sinai, and with rufidorsalis in a narrow zone, around Wadi Halfa. It has been recorded in Somaliland.^[54][55]
  • P. d. persicus, Zarudny and Kudashev, 1916, described from the Karun River in Khūzestān, Iran, is found in the western half of Iran to the south of the Elburz mountains, gradually integrading with indicus across central Iran.^[54]
  • P. d. biblicus, Hartert, 1910, described from Palestine, is found in the Middle East from the Bosphorus to the Sinai in the west and from Azerbaijan to Kuwait in the east.^[54]
• indicus group
  • P. d. hyrcanus, Zarudny and Kudashev, 1916, described from Gorgan, Iran, is found along the southern coast of the Caspian Sea from the Iranian-Azerbaijani border to Gurgan. It integrades with persicus in the Elburz mountains, and with bibilicus to the west. It is the subspecies with the smallest range.^[54]
  • P. d. bactrianus, Zarudny and Kudashev, 1916, described from Tashkent, is found in Turkestan and northern Afghanistan. It intergrades with persicus in Baluchistan and with indicus across central Afghanistan. Unlike most other House Sparrow subspecies, it is almost entirely migratory, wintering in the plains of the northern Indian subcontinent. It is found in open country rather than in settlements, which in its range are occupied by the Tree Sparrow.^[54] There is an exceptional record from Sudan.^[55]
  • P. d. parkini, Whistler, 1920, described from Srinagar, Kashmir, is found in the western Himalayas from the Pamir Mountains to southeastern Nepal. It is migratory, like bactrianus.^[13][54]
  • P. d. indicus, Jardine and Selby, 1831, described from Bangalore, is found in the Indian subcontinent south of the Himalayas, in Sri Lanka, eastern Iran, southwestern Arabia and western Southeast Asia.^[13][54]
  • P. d. hufufae, Ticehurst and Cheeseman, 1924, described from the town of Al-Hofuf in Saudi Arabia, is found in northeastern Arabia.^[54][56]
  • P. d. rufidorsalis, Brehm, 1855, described from Khartoum in Sudan, is found in the Nile valley from Wadi Halfa south to Renk in Sudan.^[54][55] It has also been introduced to Mohéli in the Comoros.^[57]

In North America and Hawaii, House Sparrow populations are more differentiated than those in Europe.^[6] This variation follows predictable patterns, with birds at higher latitudes being larger and those in arid areas being paler.^[7][58][59] However, it is not clear how much this is caused by evolution or by environment.^{[60][61][62][63]} Similar observations have been made in New Zealand,^[64] and in South Africa.^[65] Introduced House Sparrow populations may be distinct enough to merit subspecies status,^[25] and American ornithologist Harry Church Oberholser even gave the subspecies name plecticus to the paler birds of western North America in his 1974 Bird Life of Texas.^[58]

Distribution and habitat

House Sparrows flocking and chirping together in Germany

The House Sparrow originated in the Middle East and spread, along with agriculture, to most of Eurasia, and parts of North Africa.^[66] Since the mid-nineteenth century, it has spread throughout much of the world, mostly due to deliberate introductions but also through natural dispersal and shipborne travel.^[67] The House Sparrow has also greatly extended its range in northern Eurasia since the 1850s,^[68] and continues to do so, as is shown by the colonisations, both around 1990, of Iceland and Rishiri Island.^[69]

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, making it the most widely distributed wild bird on the planet.^[70] The House Sparrow has become highly successful in most parts of the world where it has been introduced. This is mostly due to its early adaptation to living with humans, and its adaptability to a wide range of conditions.^[71][72] Other factors may include its robust immune response.^[73] When introduced, the House Sparrow spreads quickly, sometimes at the rate of over 140 miles per year.^[74] In many parts of the world it has become a pest, and a threat to many native bird species.^[75][76] A few introductions have died out or been of limited success, such as those to Greenland and Cape Verde.^[77]

The first of many successful introductions to North America occurred when fifty pairs from England were released in Brooklyn, New York, in 1852.^[78][79] It now occurs from Northwest Territories to Darién Province,^[2] and it is one of the most abundant birds in North America.^[75] The House Sparrow was first introduced to Australia in 1863 at Melbourne and is a common pest throughout eastern Australia,^[77] but has been prevented from establishing itself in Western Australia, where every House Sparrow found in the state is killed.^[80] House Sparrows were introduced in New Zealand in 1859, and from there reached many of the Pacific islands, including Hawaii.^[81] In southern Africa birds of both the European subspecies domesticus and the Indian subspecies indicus were introduced around 1900. Birds of domesticus ancestry are confined to a few towns, while indicus birds have spread rapidly, reaching Tanzania in the 1980s. Despite this success, native relatives such as the Cape Sparrow also occur in towns, competing successfully with it.^[77][82] In South America, it was first introduced near Buenos Aires around 1870, and quickly became common in most of the southern part of the continent. It now occurs almost continuously from Tierra del Fuego to the fringes of Amazonia, with isolated populations as far north as coastal Venezuela.^[77][83][84]

The House Sparrow is closely associated with human habitations and cultivation.^[85] It is not the obligate commensal of humans some have suggested it is, as Central Asian birds usually breed away from humans in open country,^[86] and birds elsewhere are found away from humans.^[85][87][88] The only habitats in which the House Sparrow is not found are dense forest and tundra. It is, however, well adapted to living around humans. It frequently lives and even breeds indoors, especially in factories, warehouses, and zoos.^[85] It has been recorded breeding in a coal mine 640 m (2,100 ft) below ground,^[89] and feeding on the Empire State Building's observation deck at night.^[90] It reaches its greatest densities in urban centers, but its reproductive success is greater in suburbs, where insects are more abundant.^[85][91] On a larger scale, it is most abundant in wheat-growing areas such as the Midwestern United States.^[92] In most of eastern Asia the House Sparrow is entirely absent, replaced by the Eurasian Tree Sparrow.^[93] 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 Maud Doria Haviland described as "random, or even capricious".^[94] It tolerates a variety of climates, but prefers drier conditions, especially in moist tropical climates.^[77][85] It has a number of adaptations to dry areas, including a high salt tolerance^[95] and an ability to survive without water by ingesting berries.^[96] In most of its range the House Sparrow is extremely common, despite some declines,^[1] but in marginal habitats such as rainforest or mountain ranges, its distribution can be spotty.^[85]

Behaviour

The House Sparrow often bathes in water (at left) or in dust (at right)

The House Sparrow is a very social bird. It is gregarious at all seasons when feeding, often forming flocks with other types of bird.^[97] It also roosts communally, its nests are usually grouped together in clumps, and it engages in a number of social activities, such as dust and water bathing, and "social singing", in which birds call together in bushes.^[98][99] The House Sparrow feeds mostly on the ground, but it flocks in trees and bushes.^[98] For the larger part it is sedentary, rarely moving more than a few kilometres.^[100] There is limited migration in sedentary populations, with mountain birds moving to lower altitudes and some young birds dispersing long distances, especially on coasts.^[98][101] In addition, two subspecies, bactrianus and parkini, are predominately migratory and unlike the birds in sedentary populations that migrate, prepare for migration by putting on weight.^[98] Non-breeding House Sparrows roost in large groups in trees, gathering some time before and calling together.^[98] At feeding stations and at the nest, the female House Sparrows are dominant, despite their smaller size.^[102][103]

Feeding

Female foraging in Germany

As an adult, the House Sparrow mostly feeds on the seeds of cereals and weeds, but it is opportunistic and adaptable, and eats whatever foods are available.^[104] It can perform complex and unusual tasks to obtain food, such as opening automatic doors to enter supermarkets,^[105] clinging to hotel walls to watch vacationers on their balconies,^[106] and nectar robbing kowhai flowers.^[107] In common with many other birds, the House Sparrow requires grit to digest the hard seeds 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.^[108][109]

Several studies of the House Sparrow in temperate agricultural areas have found the proportion of seeds in its diet to be about 90 percent.^{[104][110][111]} It will eat almost any seeds, but where it has a choice, it prefers oats and wheat.^[112] In urban areas, the House Sparrow feeds largely on food provided directly or indirectly by humans, such as bread, though it prefers raw seeds.^[111][113] The House Sparrow also eats berries and fruits, and it can survive without water in arid areas by ingesting moisture from berries.^[96] In temperate areas, the House Sparrow has an unusual habit of tearing flowers, especially yellow ones, in the spring.^[114]

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.^[104] Nestling House Sparrows are fed mostly on insects until about fifteen days after hatching.^[115] They are also given small quantities of seeds, spiders, and grit. In most places, grasshoppers and crickets are most the abundant foods of nestlings.^[116] True bugs, ants, sawflies, and beetles are also important, but House Sparrows will take advantage of whatever food is most abundant to feed their nestlings.^{[116][117][118]}

Breeding

A pair of the subspecies indicus mating in Kolkata

The House Sparrow can breed in the breeding season immediately following its hatching, and sometimes attempts to do so. Some birds breeding for the first time in tropical areas are only a few months old, and retain juvenile plumage.^[119] 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.^[120] The timing of the House Sparrow's breeding season is varied, depending mostly on the availability of insects.^[121]

The House Sparrow is monogamous, and typically mates for life. Birds from pairs often engage in extra-pair copulations, with about 15 percent of House Sparrow fledgelings being unrelated to their mother's mate.^[122] Bigamy occurs, and is mostly limited by aggression between females.^[123] Male House Sparrows guard their mates carefully before breeding to avoid being cuckolded.^[124] Many birds do not find a nest and a mate, and instead may serve as helpers for mated pairs, a role which increases the chances of being chosen to replace a lost mate. Lost mates of both sexes can be quickly replaced during the breeding season.^[125][126] The formation of a pair and the bond between the two birds is related to the holding of a nest site, though birds of a pair can recognise each other away from the nest.^[121] Before the breeding season, unmated males take up a nesting site and call incessantly to attract females. When a female approaches a displaying male, the male displays by drooping and shivering his wings, pushing up his head, raising and spreading his tail, and displaying his black bib.^[121] The male then tries to mate with the female, who adopts a threatening posture and attacks him before flying away. The male then flies after the female and displays in front of her, attracting other males, who also display to her.^[121] These other males usually do not mate with the female, though this has been recorded once.^[127] When the female is ready to copulate, she solicits to the male by giving a soft dee-dee-dee call. Pairs copulate frequently and the male mounts the female repeatedly.^[121]

Female bringing food for young in a nest made in a tree hole in California

The House Sparrow's nesting sites are varied, but it prefers the shelter of a hole. Nests are most frequently built in the eaves and other crevices of houses. Holes in cliffs and banks, or in tree cavities are also used.^[128][129] It sometimes excavates its own nests in sandy banks or rotten branches, but it more frequently uses the nests of other birds: those of swallows in banks and cliffs, and old woodpecker cavity nests.^[128] It usually uses unused nests, though it sometimes usurps actively used nests.^[128][130] The House Sparrow nests more commonly in tree holes in North America than in Europe,^[128] and as such it competes with bluebirds and other North American cavity nesters, contributing to their declines in population.^[75] Especially in warmer areas, the House Sparrow also builds its nests in the open, on the branches of trees, especially evergreens and hawthorns; or in the nests of large birds such as storks or magpies.^{[121][128][131]} In open nesting sites, breeding success tends to be lower, since breeding begins late and the nest can easily be destroyed or damaged by storms.^[128][132] Less common nesting sites used by the House Sparrow include streetlights and neon signs, favoured due to their warmth; and the old open-topped nests of other songbirds, which are domed over.^[128][129]

The nest is usually domed, though it sometimes is not roofed over in enclosed sites.^[128] It has an outer layer of stems and roots, a middle layer of dead grass and leaves, and a lining of feathers, as well as paper and other soft materials.^[129] Nest typically have external dimensions of 20 × 30 cm,^[121] but their size varies greatly.^[129] The building of the nest is initiated by the unmated male, who begins construction while displaying to females. The female assists in building, but is less active than the male. Some nest building occurs throughout the year, especially after moult in autumn.^[128] In colder areas House Sparrows build specially created roost nests, or roost in streetlights, to avoid losing heat during the winter.^[128][133] The House Sparrow does not keep territories, but it defends its nest aggressively against intruders of the same sex.^[128]

The House Sparrow's nests support a wide range of scavenging insects, including nest flies such as Neottiophilum praestum, and the species of Protocalliphora,^[134] and over 1,400 species of beetle.^[135]

Eggs in a nest

Clutches usually contain four or five eggs, though clutches with only one egg or with as many as ten eggs have been recorded.^[136] Clutch size is larger at poleward latitudes and smaller near the sea and on islands. Central Asian House Sparrows, which migrate and have only one clutch a year, have an average of 6.53 eggs in a year. Variation in clutch size is caused by environmental and seasonal conditions, female age, breeding density, but is probably not hereditary.^[137] Some intraspecific brood parasitism occurs, and instances of unusually large numbers of eggs in a nest may be the result of females laying eggs in the nests of their neighbours. Such foreign eggs are sometimes recognised and ejected by females.^[136][138] The House Sparrow is a victim of interspecific brood parasites, but only rarely, since it usually uses nests in holes too small for parasites to enter, and it feeds its young foods unsuitable for young parasites.^[139][140] The House Sparrow has been recorded as a brood parasite of the Cliff Swallow once.^[138][141]

A female feeding a chick

The eggs are white, bluish-white or greenish-white, spotted with brown or grey.^[2] Subelliptical in shape,^[7] they range from 20–22 millimetres (0.79–0.87 in) in length and 14–16 millimetres (0.55–0.63 in) in width,^[2] and have an average mass of 2.9 grams (0.10 oz),^[142] and an average surface area of 9.18 square centimetres (1.423 sq in).^[143] Eggs from the tropical subspecies are distinctly smaller.^[144][145] Eggs begin to develop with the deposition of yolk in the ovary a few days before ovulation. In the day between ovulation and laying, egg white forms, followed by eggshell.^[146] Eggs laid later in a clutch are larger, as are those laid by larger females, and egg size is hereditary. Eggs decrease slightly in size from laying to hatching.^[147] The yolk comprises 25 percent of the egg, the egg white 68 percent, and the shell 7 percent. Eggs are watery, being 79 percent liquid, and otherwise mostly protein.^[148]

The female develops a brood patch of bare skin and plays the main part in incubating the eggs. The male helps, but he can only cover the eggs rather than truly incubating them. The female spends the night incubating during this period, while the male roosts near the nest.^[136] 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.^{[7][121][149]}

Survival

A male being eaten by a cat, one of the primary predators of the House Sparrow

The House Sparrow's main predators are cats and birds of prey, but many other predators feed on the House Sparrow, including corvids, smaller squirrels,^[150] and even humans, as the House Sparrow has been consumed by humans in many parts of the world, and still is in parts of the Mediterranean.^[151] Most species of bird of prey have been recorded preying on the House Sparrow in places where there are extensive records. Accipiters and the Merlin in particular are major predators, though cats likely make a greater impact on House Sparrow populations.^[150] The House Sparrow is also a common victim of roadkill; on European roads, it is the species most frequently found dead.^[152]

The House Sparrow is host to a huge number of parasites and diseases, and the effect of most is unknown. Ted R. Anderson listed thousands, noting that his list was incomplete.^[153] Many of the diseases hosted by the House Sparrow are also present in humans and their domestic animals, for which the House Sparrow acts as a reservoir host.^[154] Arboviruses such as the West Nile virus, which most commonly infect insects and mammals, survive winters in temperate areas by going dormant in birds such as the House Sparrow.^[153][155] The commonly recorded bacterial pathogens of the House Sparrow are often those common in humans, and they include Salmonella and Escherichia coli.^[156] Salmonella is common in the House Sparrow, and a comprehensive study of House Sparrow disease found it in 12.9 percent of sparrows tested. Salmonella epidemics in the spring and winter can kill large numbers of sparrows.^[153] The House Sparrow hosts avian pox and avian malaria, which it has spread to the native forest birds of Hawaii.^[157] There are a few records of disease extirpating House Sparrow populations, especially from Scottish islands, but this seems to be rare.^[158]

The House Sparrow is infested by a number of external parasites, which usually cause little harm to adult sparrows. In Europe, the most common mite found on sparrows is Proctophyllodes, the most common ticks are Argas reflexus and Ixodes arboricola, and the most common flea on the House Sparrow is Ceratophyllus gallinae. A number of chewing lice occupy different niches on the House Sparrow's body. Menacanthus lice occur across the House Sparrow's body, where they feed on blood and feathers, while Brueelia lice feed on feathers and Philopterus fringillae occurs on the head.^[134]

In the adult House Sparrow, annual survival is between 45 and 65 percent.^[159] After fledgeing and leaving the care of its parents, the young House Sparrow has a high mortality rate, which lessens as it grows older and more experienced. Only about 20 to 25 percent of birds hatched survive to their first breeding season.^[160] The oldest known wild House Sparrow lived for nearly two decades; it was found dead 19 years and 9 months after it was ringed in Denmark.^[161] The oldest recorded captive sparrow lived for twenty-three years.^[162] The typical ratio of males to females is uncertain due to problems in collecting data, but a very slight preponderance of males at all ages seems to be the usual situation.^[163]

Relationships with humans

A female in Australia

The House Sparrow is closely associated with humans. Usually, it is regarded as a pest, since it consumes agricultural products and spreads disease to humans and their domestic animals.^[164] Even birdwatchers often hold it in little regard because of its molestation of other birds.^[75] In most of the world the House Sparrow is not protected by law. Attempts to control House Sparrows include the trapping, poisoning, or shooting of adults; the destruction of their nests and eggs; or less directly, blocking nest holes and scaring off sparrows with noise, glue, or porcupine wire.^[165]

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 on the IUCN Red List.^[1] However, populations are declining in many parts of the world.^{[166][167][168]} These declines were first noticed in the United States, where they were initially attributed to the spread of the House Finch, but have been most severe in Western Europe.^[169][170] Declines have not been universal, as no serious declines have been reported from Eastern Europe, but they have occurred in Australia, where the House Sparrow is a recently introduced species.^[171] In the Netherlands, the House Sparrow is even considered an endangered species,^[172] and the population has dropped by half since the 1980s.^[91] In Britain, populations peaked in the early 1970s,^[173] but have since declined by 68 percent overall,^[174] and over 90 percent in urban areas.^[175] In London, the House Sparrow almost disappeared from the central city.^[175] These declines are not unprecedented, as similar reductions in population occurred when the internal combustion engine replaced the horse in the 1920s and a major source of food in the form of spillage was lost.^[176][177]

Various causes for the dramatic decreases in population have been proposed, including predation,^[178] electromagnetic radiation from mobile phones,^[179] and diseases.^[180] A shortage of nesting sites is probably a factor, and conservation organisations have encouraged the use of special nest boxes for sparrows.^{[180][181][182][183]} The main cause of the decline seems to be nestling starvation due to an insufficient supply of insect food.^[180][184] The decline in the insect population is caused by an increase of monoculture crops, the heavy use of pesticides,^{[185][186][187]} the replacement of native plants in cities with introduced plants and parking areas,^[188][189] and possibly the introduction of unleaded petroleum, which produces toxic compounds such as methyl nitrite.^[190] Protecting insect habitats on farms,^[191] and planting native plants in cities benefit the House Sparrow, as does establishing urban green spaces.^[192][193]

To many people across the world, the House Sparrow is the most familiar wild animal and, because of this familiarity, it is frequently used to represent the common and vulgar, or the lewd.^[194] One of the reasons for the introduction of House Sparrows throughout the world was their association with the European homeland of many immigrants.^[79] Sparrows are referred to in religious texts, and in ancient literature, most notably in the New Testament and in Catullus's poems about Lesbia. These references may not specifically refer to the House Sparrow, or even to small, seed-eating birds, but later writers who were inspired by these texts often had the House Sparrow in mind.^[194][195]

The House Sparrow is only represented in ancient Egyptian art very rarely, but an Egyptian hieroglyph is based on it, the sparrow hieroglyph:The symbol had no phonetic value and was used as a determinative in words to indicate small, narrow or bad.^[196]

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