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. The domestic pigeon, often called "Columba livia domestica", which includes about 1,000 different breeds, is descended from this species. Escaped domestic pigeons are the origin of feral pigeons around the world. Both forms can vary widely in the colour and pattern of their plumage unlike their wild ancestor, being red, brown, checkered, uniformly coloured, or pied.
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.
Taxonomy and systematics
The official standard English name is rock dove, as given by the International Ornithological Congress.
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",James A. Jobling. Helm Dictionary of Scientific Bird Names. Bloomsbury Publishing p. 114 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. Pigeon chicks are called "squabs". Note that members of the pigeon genus Petrophassa and the speckled pigeon (Columba guinea), also have the common name "rock pigeon".
Subspecies Nine subspecies are recognised: C. l. livia Gmelin, JF, 1789 – west, central Europe, north Africa to central Asia C. l. gymnocycla Gray, GR, 1856 – Mauritania and Senegal to south Mali and Ghana C. l. targia Geyr von Schweppenburg, 1916 – north Mali and south Algeria to central Sudan C. l. schimperi Bonaparte, 1854 – east Egypt, south Sudan and Eritrea C. l. dakhlae Meinertzhagen, R, 1928 – west Egypt C. l. palaestinae Zedlitz, 1912 – Sinai Peninsula (Egypt) to Syria, to west and south Arabian Peninsula C. l. gaddi Zarudny & Loudon, 1906 – east Turkey to Uzbekistan, to west and north Afghanistan C. l. neglecta Hume, 1873 – west Pakistan and east Afghanistan to the Himalayas C. l. intermedia Strickland, 1844 – south India and Sri Lanka
Description
Millennia of domestication have greatly altered the rock dove in many regions. Domestic and Feral pigeons, which arose through selective breeding, not originating naturally, have significant variation in plumage from the natural wild birds. 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. Weight for wild or feral rock doves ranges from , though overfed domestic and semi-domestic individuals can exceed normal weights. For standard measurements, the wing chord is typically around , the tail is , the bill is around , and the tarsus is .
This species has dark bluish-grey head, neck, and chest feathers with glossy greenish to reddish-purple iridescence along its neck feathers. The white lower back of the pure rock dove is its best identification characteristic; the two black bars on its pale grey wings are also distinctive. The tail has a black band on the end, and the outer web of the tail feathers are margined with white. The iris is red-brown. The eyelids are grey with a very narrow bluish-grey to grey-white eye ring (wider in domesticated and feral birds). The bill is grey-black with a small off-white cere (with domesticated and feral birds having a much larger cere). The feet are red to pink.
The adult female is almost identical in outward appearance to the male, but the iridescence on her neck is less intense and more restricted to the rear and sides, whereas that on the breast is often very obscure. Young females show little lustre and are duller.
When circling overhead, the white underwing of the bird becomes conspicuous. In its flight, behaviour, and voice, which is more of a dovecot coo than the phrase of the wood pigeon, it is a typical Columba pigeon. Although it is a strong flier, it also glides frequently, holding its wings in a very pronounced V shape as it does.
The various subspecies are similar to the nominate, but can be differentiated: C. l. livia, the nominate subspecies, has mid-grey mantle plumage, and a relatively short tail. C. l. gymnocycla is smaller and very much darker than the nominate. It is almost blackish on the head, rump and underparts with a white back and the iridescence of the nape extending onto the head. C. l. targia is slightly smaller than the nominate, with similar plumage, but the back is concolorous with the mantle instead of white. C. l. schimperi closely resembles C. l. targia, but has a distinctly paler mantle. C. l. dakhlae is smaller and much paler than the nominate. C. l. palaestinae is slightly larger than C. l. schimperi and has darker plumage. C. l. gaddi is larger and paler than C. l. palaestinae, with which it intergrades in the west. C. l. neglecta it is similar to the nominate in size but darker, with a stronger and more extensive iridescent sheen on the neck. It intergrades with C. l. gaddi in the south. C. l. intermedia is similar to C. l. neglecta but darker, with a less contrasting back.
There have been numerous skeletal descriptions of the rock dove and the associated muscles including those of the eye, jaw, neck, and throat. The skull is dominated by the rostrum, eye socket, and braincase. The quadrate bone is relatively small and mobile and connects the rest of the cranium to the lower jaw. The latter has an angled shape in lateral view because the long-axis of the front half of the lower jaw is at a 30° angle to the back half. Beneath the skull, the hyoid skeleton involves three mid-line structures and a pair of elongate structures that stem from between the junction of the back two structures. The anterior structure (the paraglossum or entoglossum) is unpaired and shaped like an arrowhead.
Pigeons feathers have two types of melanin (pigment), eumelanin and pheomelanin. A study of melanin in the feathers of both wild rock and domestic pigeons, of different colour types and known genetic background, measured the concentration, distribution and proportions of eumelanin and pheomelanin and found that gene mutations affecting the distribution, amounts and proportions of pigments accounted for the greater variation of colour in domesticated birds than in their wild relations. Eumelanin generally causes grey or black colours, while pheomelanin results in a reddish-brown colour. Other shades of brown may be produced through different combinations and concentrations of the two colours. 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. Variations include an alarm call, a nest call, and noises made by juveniles. 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.
Osmoregulation
Osmoregulation in rock doves is complicated by the formation of amine groups, as proteins are broken down for energy. 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.
Distribution and habitat The natural distribution of the rock dove is restricted to a resident range in western and southern Europe, North Africa, and extending into South Asia. They were introduced into most of the rest of the world aboard European ships from 1603 onwards. 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. Fossil evidence suggests the rock dove originated in southern Asia, and skeletal remains, unearthed in Israel, confirm its existence there for at least 300,000 years. However, this species has such a long history with humans that it is impossible to identify its original range exactly.