Bird N°4. House Sparrow - Passer domesticus
In the UK the bird charity RSPB (Royal Society for the Protection of Birds) have suggested that populations of the House Sparrow are in severe decline. Estimates suggest that the population dropped by 71% between 1977 and 2008, with both rural and urban populations have suffered, however the population is estimated to be between 2.1 - 3.7 Million breeding pairs. While this has been reported as a UK decline the House Sparrow are the most numerous bird species in my garden and I'm not alone, the Breeding Bird Survey data indicated that the populations of Scotland, Wales and Northern Ireland have all increased. Having said that the decline in House Sparrow numbers does appear to be widespread over much of Western Europe and they have disappeared completely from some parts of England. Many reasons have been suggested including the widespread use of garden pesticides resulting in an absence of insects needed by newborn sparrows, even the disappearance of hens from many farmyards and back gardens must have reduced the availability of food. Let's hope that England and Western Europe can get a grip on whatever is that is causing the decline of the House Sparrow and at least halt that decline.
The House Sparrow (Passer domesticus) is obviously a member 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 in) and a weight of 24–39.5 grams (0.85–1.39 oz). 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 occurs naturally in 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. The House Sparrow feeds mostly on the seeds of grains and weeds, and insects, and can perform complex and unusual tasks to obtain food. The predators of the House Sparrow include domestic cats, hawks, owls and many other predatory birds and mammals.
The House Sparrow is a chunky bird, typically about 16 centimetres (6.3 in) long, ranging from 14–18 centimetres (5.5–7.1 in). It has a large rounded head, a short tail, and a stout bill. In weight, the House Sparrow ranges from 24–39.5 grams (0.85–1.39 oz). Weight varies by sex, with females usually smaller than males. The median weight on the European continent for both sexes is about 30 grams (1.1 oz), and in more southerly subspecies is around 26 grams (0.92 oz). Younger birds are smaller, males are larger during the winter, and females are larger during the breeding season. 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.
The plumage of the House Sparrow is mostly different shades of grey and brown. The sexes differ: the female is mostly buff, and the male has bolder markings and a reddish back. The male has a dark grey crown from the top of its bill to its back, and chestnut brown 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 covers, 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, a hypothesis which has led to a "veritable 'cottage industry'" of studies, which have only conclusively shown that patches increase in size with age. The female has no black on head or throat, nor a grey crown, and its upperparts are streaked with brown. The juvenile is similar to the female but deeper brown, and the white is replaced by buff; its beak is pink to dull yellow. There is some variation in the twelve subspecies of House Sparrow, but I'm not getting into those, because frankly without having examples to compare side by side they are extremely difficult to spot, indeed some are just larger while otherwise identical.
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 often can not be distinguished from other birds, and is nearly identical to the females of the Spanish Sparrow and Italian Sparrow. 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.
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, due chiefly to deliberate introductions, but also through natural dispersal and shipborne travel. 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. The House Sparrow has also 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.
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. Other factors may include its robust immune response, compared to the Eurasian Tree Sparrow. When introduced, the House Sparrow can spread quickly, sometimes at the rate of over 140 miles per year. In many parts of the world it has become a pest, and a threat to native bird species. A few introductions have died out or been of limited success, such as those to Greenland and Cape Verde.
The first of many successful introductions to North America occurred when birds from England were released in New York City, in 1852. It now occurs from the Northwest Territories to southern Panama, and it is one of the most abundant birds in North America. The House Sparrow was first introduced to Australia in 1863 at Melborne and is common throughout eastern Australia, but has been prevented from establishing itself in Western Australia, where every House Sparrow found in the state is killed. House Sparrows were introduced in New Zealand in 1859, and from there reached many of the Pacific islands, including Hawaii. 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. 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.
The House Sparrow is closely associated with human habitations and cultivation. 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, and birds elsewhere are found away from humans. The only habitats in which the House Sparrow does not occur are dense forest and tundra. Well adapted to living around humans, it frequently lives and even breeds indoors, especially in factories, warehouses, and zoos. It has been recorded breeding in an English coal mine 640 metres (2,100 ft) below ground, and feeding on the Empire State Building's observation deck at night. It reaches its greatest densities in urban centres, but its reproductive success is greater in suburbs, where insects are more abundant. On a larger scale, it is most abundant in wheat growing areas such as the Midwestern United States. It tolerates a variety of climates, but prefers drier conditions, especially in moist tropical climates. It has a number of 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 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.
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 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. The House Sparrow feeds mostly on the ground, but it flocks in trees and bushes. Non-breeding House Sparrows roost in large groups in trees, gathering some time before and calling together. At feeding stations and nests, female House Sparrows are dominant, despite their smaller size.
Most birds do not move more than a few kilometres. However, there is limited migration in all regions. Some young birds disperse long distances, especially on coasts, and mountain birds move to lower altitudes in winter. In addition, 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.
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. It can perform complex and unusual 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 hard seeds it eats. Grit can be either stone, often grains of masonry, or the shells of eggs or snails; oblong and rough grains are preferred.
Several studies of the House Sparrow in temperate agricultural areas have found the proportion of seeds in its diet to be about 90 percent. It will eat almost any seeds, but where it has a choice, it prefers oats and wheat. In urban areas, the House Sparrow feeds largely on food provided directly or indirectly by humans, such as bread, though it prefers raw seeds. The House Sparrow also eats some plant matter besides seeds, including buds, berries, and fruits such as grapes and cherries. In temperate areas, the House Sparrow has an unusual habit of tearing flowers, especially yellow ones, in the spring.
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 most the 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 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 retain 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. The timing of the House Sparrow's breeding season varies between locations and years and may depend on the availability of insects, needed for egg formation and feeding nestlings.
Before the breeding season, males take up their nesting sites, by frequently beside them. Unmated males start nest construction and call particularly frequently to attract females. When a female approaches a displaying male, 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. Pairs copulate frequently and the male mounts the female repeatedly.
The House Sparrow is monogamous, and typically mates for life. Birds from pairs often engage in extra-pair copulations, so about 15 percent of House Sparrow fledgelings 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 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.
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. 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 tree cavity nests. It usually uses unused nests, though it sometimes usurps actively used nests. The House Sparrow nests more commonly in tree holes in North America than in Europe, and as such it competes with bluebirds and other North American cavity nesters, contributing to their declines in population. Especially in warmer areas, the House Sparrow may build its nests in the open, on the branches of trees, especially evergreens and hawthorns; or in the nests of large birds such as storks ormagpies. 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. Less common nesting sites used by the House Sparrow include streetlights and neon signs, favoured for their warmth; and the old open-topped nests of other songbirds, which are domed over.
The nest is usually domed, though it sometimes is not roofed over in enclosed sites. 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. Nest typically have external dimensions of 20 × 30 cm (8 × 12 in), but their size varies greatly. The building of the nest is initiated by the unmated male 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. In colder areas House Sparrows build specially created roost nests, or roost in streetlights, to avoid losing heat during the winter. The House Sparrow does not keep territories, but it defends its nest aggressively against intruders of the same sex.
The House Sparrow's nests support a wide range of scavenging insects, including nest flies such as Neottiophilum praestum, Protocalliphora blowflies, and over 1,400 species of beetle.
Clutches usually contain four or five eggs, though clutches with only one egg or with as many as ten eggs have been recorded. 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, and breeding density. 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. 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. The House Sparrow has been recorded as a brood parasite of the American Cliff Swallow once.
The eggs are white, bluish-white or greenish-white, spotted with brown or grey. Subelliptical in shape, they range from 20–22 millimetres (0.79–0.87 in) in length and 14–16 millimetres (0.55–0.63 in) in width, have an average mass of 2.9 grams (0.10 oz), and an average surface area of 9.18 square centimetres (1.423 sq in). Eggs from the tropical subspecies are distinctly smaller. 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. 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. 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.
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 incubating 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 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 the first days. Later, the droppings are moved up to 20 metres (66 ft) away from the nest. The eyes open after about four days and at an age of about 8 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 the young until they can sustain themselves. All the young in the nest leave it in 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.
House Sparrow's main predators are cats and birds of prey, but many other predators feed on the House Sparrow, including corvids, smaller squirrels, 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. 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. The House Sparrow is also a common victim of roadkill; on European roads, it is the bird most frequently found dead.
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. The commonly recorded bacterial pathogens of the House Sparrow are often those common in humans, and include Salmonella and Escherichia coli. Salmonella is common in the House Sparrow, and a comprehensive study of House Sparrow disease found it in 13 percent of sparrows tested. Salmonella epidemics in the spring and winter can kill large numbers of sparrows. The House Sparrow hosts avian pox and avian malaria, which it has spread to the native forest birds of Hawaii. Many of the diseases hosted by the House Sparrow are also present in humans and domestic animals, for which the House Sparrow acts as a reservoir host. 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. There are a few records of disease extirpating House Sparrow populations, especially from Scottish islands, but this seems to be rare.
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.
In adult House Sparrows, annual survival is between 45 and 65 percent. After fledgeing and leaving the care of their parents, young House Sparrows have a high mortality rate, which lessens as they grow older and more experienced. Only about 20 to 25 percent of birds hatched survive to their first breeding season. 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. The oldest recorded captive House Sparrow lived for 23 years. 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.
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