Rock dove - WikiHQ

The rock dove (Columba livia), also known as the common pigeon or rock pigeon (but see also Petrophassa), is a member of the bird family Columbidae (doves and pigeons). In common usage, it is often simply referred to as the "pigeon", although the rock dove is the wild form of the bird; the pigeons familiar to most people are the domesticated forms of the wild rock dove.

Wild rock doves are uniformly pale grey with two black bars on each wing, with few differences being seen between males and females; i.e. they are not strongly sexually dimorphic.

Habitats include various open and semi-open environments where they are able to forage on the ground. Cliffs and rock ledges are used for roosting and breeding in the wild. Originating in Southern Europe, North Africa, and Western Asia, when including their domestic and feral descendants, they are an example of a least-concern species per IUCN among birds, being abundant with an estimated population of 17 to 28 million wild and feral birds in Europe alone and up to 120 million worldwide.

The rock dove was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Systema Naturae written by Carl Linnaeus. He placed it with all the other doves and pigeons in the genus Columba and coined the binomial name Columba livia. The genus name Columba is the Latin word meaning "pigeon, dove", whose older etymology comes from the Ancient Greek κόλυμβος (kólumbos), "a diver", hence κολυμβάω (kolumbáō), "dive, plunge headlong, swim". Aristophanes (Birds 304) and others use the word κολυμβίς (kolumbís), "diver", for the name of the bird, because of its swimming motion in the air. The specific epithet livia is a Medieval Latin variant of livida, "livid, bluish-grey"; this was Theodorus Gaza's translation of Greek péleia, "dove", itself thought to be derived from pellós, "dark-coloured".

No original material was designated by Gmelin in his description of the species, and consequently a neotype specimen, from Fair Isle in Scotland, has been designated to define the species and its nominate subspecies C. l. livia.

Its closest relative in the genus Columba is the hill pigeon, followed by the snow, speckled, and white-collared pigeons. This wild type is endangered in many areas; the nominate subspecies C. l. livia persists most notably in the far north and west of Scotland, most strongly so in the Outer Hebrides.

The adult of the nominate subspecies of the rock dove is long with a wingspan. For standard measurements, the wing chord is typically around , the tail is , the bill is around , and the tarsus is . The skull is dominated by the rostrum, eye socket, and braincase. Darker birds may be better able to store trace metals in their feathers due to their higher concentrations of melanin, which may help mitigate the negative effects of the metals, the concentrations of which are typically higher in urban areas.

Vocalisations

The call is a soft, slightly wavering, coo "crruoo-u", similar to feral pigeons. When displaying, songs are partly sexual, partly threatening. They are accompanied by an inflated throat, tail fanning, strutting, and bowing. The alarm call, given at sight of predators, is a grunt-like oorhh.

They secrete these amine groups in uric acid, which has the advantage of releasing nitrogen while using only moderate amounts of water, but also has the disadvantage of using much energy, due to uric acid's complex chemical composition.

All Columbids, which includes rock doves, can lower their water intake when food is scarce, and vice versa, as water is needed to excrete toxins, yet maintaining bodily water balance is vital for survival. Although rock doves inhabit arid environments, research shows that their large flight range allows them to reach distant water sources, making bodily water conservation less critical for them.

Unlike other birds, rock doves use their kidneys to maintain homeostatic balance, instead of their salt gland, as kidneys can filter out blood, reabsorb ions and water, and secrete Uric acid. Additionally, the kidneys of birds contain a medullary region, and a cortical region, similar to mammalian kidneys. However, the nephrons of birds cannot directly produce urine that is hyperosmotic to the blood, unlike mammals. Despite this, nephrons with the loop of Henle use a countercurrent mechanism, which allows blood to become hyperosmotic in the collecting duct.

Eggshell gas exchange and water loss

Birds' eggs are very susceptible to variations in temperature and humidity, as the gas exchange that occurs while an embryo is growing leads to water loss, which in turn can kill the embryo via desiccation. To regulate this, the parents regularly incubate their eggs when the environment changes rapidly, or the environment is very dry, although very humid environments can inhibit respiration. Their eggshells contain pore-like areas, which allow water to diffuse in and out, preventing desiccation of the embryo due via a high rate of water retention. However, thinner eggshells can cause decreases in pore length, increases in conductance and pore area, and decreases in mechanical restriction of the embryo. When including feral birds, the species has a very large range, with an estimated global extent of occurrence of . It has a large global population, including an estimated 17 to 28 million individuals in Europe.

Non-vocal sounds include a loud flapping noise at take-off, feet stamping, hisses, and beak snapping. Wings may also be clapped during flights, usually during display fights or after copulation. Juveniles particularly snap their bills, usually to respond to nest invasion. The foot stomping appears deliberate, though for what purpose is unclear. Foot stamping is done with a certain foot first, showing that rock doves have "footedness", similar to human handedness. At first, the female invariably walks or flies a short distance away and the male follows her until she stops. At this point, he continues the bowing motion and very often makes full- or half-pirouettes in front of the female. The male then proceeds to feed the female by regurgitating food, as they do when feeding the young. The male then mounts the female, rearing backwards to be able to join their cloacae. The mating is very brief, with the male flapping his wings to maintain balance on top of the female. Current evidence suggests that wild, domestic and feral pigeons mate for life, although their long-term bonds are not unbreakable. They are socially monogamous, but extra-pair matings do occur, often initiated by males.

The nest is a flimsy platform of straw and sticks, laid on a ledge, under cover.

A rock dove's lifespan ranges from 3–5 years in the wild to 15 years in captivity, though longer-lived specimens have been reported. The main causes of mortality in the wild are predators and persecution by humans.

Feeding

Rock doves are omnivorous, but prefer plant matter: chiefly fruit and grains.

thumb|A rock dove [[foraging with hill pigeons (Columba rupestris)]]

Pigeons feed on the ground in flocks or individually. Pigeon groups typically consist of "producers", which scout out food sources, and "scroungers", which follow the producers and feed on food located by them.

Preening

Pigeons primarily use powder down feathers for preening, which gives a soft and silky feel to their plumage. They have no preen gland or at times have very rudimentary preen glands, so oil is not used for preening. Rather, powder down feathers are spread across the body. These have a tendency to disintegrate, and the powder, akin to talcum powder, helps maintain the plumage.

Predators

thumb|A feral pigeon with entirely missing tail feathers

With only their flying abilities protecting them from predation, rock doves are a favoured prey item for a wide range of raptors. Peregrine falcons are significant natural predators of rock doves and quite adept at catching and feeding upon this species. Doves and pigeons in general are considered to be game birds, since many species are hunted and used for food in many of the countries in which they are native.

Their body feathers have dense, fluffy bases and are loosely attached to the skin, hence they drop out easily. When a predator catches a pigeon, large numbers of feathers are often pulled by the attacker's mouth and the pigeon may use this temporary distraction to make an escape.

Relationship to humans

The rock dove was central to Charles Darwin's discovery of evolution, and featured in four of his works from 1859 to 1872. Darwin posited that, despite wide-ranging morphological differences, the many hundreds of breeds of domestic pigeon could all be traced back to the wild rock dove; in essence human selection of pigeon breeds was analogous to natural selection.

thumb|A flock of rock doves eating grains in [[New Delhi, India. Humans often engage in bird feeding, providing rock doves with grains or breadcrumbs.]]

Rock doves often have a commensal relationship with humans, gaining both ample access to food and nesting spots in inhabited areas. Human structures provide an excellent imitation of cliff structures, making rock doves very common around human habitation. Skyscrapers, highway overpasses, farm buildings, abandoned buildings, and other human structures with ample crevices are conducive to rock dove nesting. Thus the modern range of the rock dove is due in large part to humans. Ideal human nesting attributes combine areas with tall buildings, green spaces, ample access to human food, and schools. Conversely, suburban areas which are far from city centers and have high street density are the least conducive to pigeons. Their versatility among human structures is evidenced by a population living inside a deep well in Tunisia. Domesticated pigeons are used as homing pigeons as well as food and pets. They were in the past also used as carrier pigeons, used to deliver messages in peacetime or during war. Numerous breeds of fancy pigeons of all sizes, forms, and colours have been bred.

Feral pigeons (sometimes given the invalid names "Columba livia domestica" or "Columba livia forma urbana"), also called city doves, city pigeons, or street pigeons, are descendants of domestic pigeons living independently and often unwanted by humans. They are often described as a public nuisance, being a potential reservoir of disease and cause of property damage.