Thedomestic pigeon (Columba livia domestica orColumba liviaformadomestica)^[2] is a pigeonsubspecies that was derived from the rock dove or rock pigeon. The rock pigeon is the world's oldestdomesticated bird.Mesopotamiancuneiform tablets mention the domestication of pigeons more than 5,000 years ago, as do Egyptianhieroglyphics.

Domestic pigeon
A selection of domestic pigeon breeds and colors, the result of centuries ofselective breeding[a]
Conservation status
Domesticated
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Columbiformes
Family:	Columbidae
Genus:	Columba
Species:	C. livia
Subspecies:	C. l. domestica
Trinomial name
Columba livia domestica Gmelin, 1789[1]
Synonyms
Columba domestica Columba livia rustica

Pigeons have held historical importance to humans asfood,pets,holy animals, andmessengers. Due to their homing ability, pigeons have been used to deliver messages, includingduring the world wars. Despite this,city pigeons, which areferal birds, are generally seen aspests, mainly due to theirdroppings and a reputation forspreading disease.

Despite the long history of pigeons, little is known about the specifics of their initial domestication. Whichsubspecies ofC. livia was theprogenitor of domestics, exactly when, how many times, where and how they were domesticated, and how they spread, remains unknown. Their fragile bones andsimilarity to wild birds make thefossil record a poor tool for their study. Thus most of what is known comes fromwritten accounts, which almost certainly do not cover the first stages of domestication.^[3][4][5]

Pigeons were most likely domesticated in the Mediterranean at least 2000–5000 years ago, and may have been domesticated earlier as a food source.^[6] Some research suggests that domestication occurred as early as 10,000 years ago.^[7][8]The earliest recorded mention of pigeons comes from Mesopotamia some 5,000 years ago.^[9]Pigeon Valley inCappadocia hasrock formations that were carved into ancientdovecotes.Ancient Egyptians kept vast quantities of them, and wouldsacrifice tens of thousands at a time for ritual purposes.^[10]Akbar the Great traveled with a coterie of thousands of pigeons.^{[11][12][13][14]}

The domestic pigeon was brought tothe Americas byEuropean colonists as an easy source of food and as messengers. Some sources state the species was first introduced toNorth America in 1606 atPort Royal,Nova Scotia.^[15] Although other sources citePlymouth andJamestown settlements in the early 17th century as the first place for species introduction in North America.^[16]

Around the 18th century, European interest infancy pigeons began, and breeders there greatly expanded the variety of pigeons, importing birds from the Middle East and South Asia andmixing differentbreeds to create new ones.^[4][8] Among these European fanciers wasCharles Darwin, who was famously requested to write a book on pigeons during the process of writingOn the Origin of Species. His own experiences with pigeon fancying would ultimately lead to another book;The Variation of Animals and Plants Under Domestication.^[17][11]

Because domestic and feral pigeons have extensively interbred with wild rock doves, genetically purewild-type pigeons may not exist anymore, or are nearly extinct. This frequent admixture further muddies the true origins of pigeons.^[4][5]

From a genetic perspective, there are two loose ancestralclades of pigeons, but there is striking genetic homogeneity due to frequent interbreeding and human directed cross-breeding; pigeon fanciers often do not enforce breed standards, unlike withdogs. The first ancestral clade contains pigeons withexaggerated crops, tails, and manes; the second containstumblers (the most diverse group),homing pigeons,owl pigeons, and those with exaggerated wattles.^[4] Over the millennia of human interaction with pigeons,a multitude of pigeon breeds have been created, which differ in either plumage or body structure.^{[citation needed]}

Some varieties of domestic pigeon have modified feathers called "fat quills". These feathers contain yellow, oil-like fat that derives from the same cells as powder down. This is used while preening and helps reduce bacterial degradation of feathers by featherbacilli.^[18]

Awild-type pigeon is closest inmarkings to the rock dove, which possesses agradienting,slate-grey head and body with a green-purpleiridescent neck, andash-grey wings and tail with dark, often black, barring.^[19] Due to millennia of selective breeding, including crossing with otherColumba species, domestic pigeons possess major variations in plumage; often two birds from the same clutch may be of different color. The domestic pigeon possesses 3 main colors; the wild-typeblue,brown, andash-red. This variation in color islinked to the parent's sex chromosomes; as animals with theZW chromosome system, cockbirds possess the color genes from both parents, while hens only inherit their father's color and patterns. Additionally, there is somedominance observed; ash-red is dominant over the other two base colors, while blue is dominant over brown.^[20] Recessive red is a unique color which is inherited differently from the three base ones; it is distinct from ash-red in that the bird always is a uniform chestnut color.^[21]

Another important aspect of pigeon markings is the pattern on thewing coverts, which exists in four variants; wild-typebar,check,T-check, andbarless. T-check is the most dominant pattern, followed by check, barred, and the least dominant barless pattern.^[22] Additionally, the modifiersspread anddilute affects theexpression of the color; the spread genespreads the color of the bird's tail to its entire body, while dilute lightens the bird's overall color, as if were adye beingdiluted to reduce itssaturation.^[23][24]

There are many other markings present in pigeons; among them are milky, almond, opal, dirty, indigo, grizzle, and various "stencil" and "bronzing" factors; all of which further modify the base markings of a bird. Conversely, pigeons possess multiple genetic pathways that can produce a completely white bird.^[25]

Arecessive allele in theEphB2 gene controls the crested-feather mutation in domestic pigeons.^[26] Pigeons with two copies of the crest allele grow neck and head feathers that point towards the top of the head, unlike other feathers that point towards the tail.^[27] Additionally, bacterial growth analysis suggests that crested pigeons have reduced bacterial-killing abilities due to reducedkinase activity.^[28] Pigeons mayexpress the crest gene differently depending on itsgenetic heritage; two squabs from the same brood descending from the same pair may have one bird develop a peak crest, and the other a wild-type smooth head.^[29]

Pigeons with feathers growing on their feet have differently expressed genes: a hindlimb-development gene calledPITX1 is less active than normal, and a forelimb-development gene calledTbx5 that normally develops the wings is also active in the feet, causing both feather growth and larger leg bones. The cause of these changes is a change in the regulatory sequences of DNA that control the expression of thePitx1 and theTbx5 genes, rather than mutations in the genes themselves.^[30][31] Pigeon foot feathering has been studied as a potential model for the transition from feathered to "scaled" feet innon-avian dinosaurs.^[32] It is thought that large feathers, especially flight feathers on the feet were lost in all living birds as it was too inefficient in powered flight. Domestic pigeons quickly overheated when flying with their scaled feet covered, and it is thought that the loss ofmicroraptorian-like hind-wings allowed for more efficient powered flight.^[33]

Pouter- or cropper breeds exhibity the trait of inflating theircrops with air, producing their signature "globe". This trait is inheritable and partially dominant, though cockbirds tend to exhibit this trait more than females.^[25] Some cropper breeds may have issues with passing food and water through their crops, though this problem isn't universal and can be treated by owners.^[34]

There is strong evidence that some divergences in appearance between the wild-type rock dove and domestic pigeons, such as checkered wing patterns and red/brown coloration, may be due tointrogression bycross-breeding with thespeckled pigeon.^{[35][36][37][38]}

Domestic pigeons may be crossed with the ringneck dove (Streptopelia risoria) to create offspring, but the offspring are notfertile.^[39][40]

Domestic pigeons reproduce exactly as wildrock pigeons do;^[19] settling in a safe, cool nook, building a flimsystick nest, and laying two eggs that are incubated for a little longer thantwo weeks, usually 17 to 19 days.^[3] A pigeon keeper mayselect breeding partners, but in an open loft the birds choose their own mate. Both sexes of pigeons areextremely protective of their eggs and young, and often defend them vigorously from nest predators,^[3] including their human keepers; they are defensive of theirpersonal space, and see their nests as extensions of said space.^[41]

Baby pigeons aresquabs,^[3]squeakers,^[42][43] orpeepers, the latter two beinga reference to their cry when begging for food.^[44] Initially, the squabs are fed by their parents withcrop milk, which contains high amounts of protein and fat,^[45] some breeds are bred into such debilitating forms that they may require human intervention to produce squabs successfully, which necessitates the owner to raise them themselves by feeding the chicks with special squab formula (similar toinfant formula)^[46] or byfostering them under another pair of pigeons. This may also be necessary if the parents are unable or unwilling to raise the squab.^[47][17] When fed by their parents, the squabs develop much faster than other species ofpoultry, such asquail,^[45] and fostering in human care may be more effective than using a surrogate pair of pigeons.^[47]

As the chicks grow and become more mobile and alert, their parents transition them to their adult food ofseeds and grains. A pigeon hen may start a new clutch before her previous one has fledged, in which case her mate raises the previous clutch on his own.^[48][19] Pigeons reach their adult size around four weeks of age,^[45][49][48] and after fledging the chicks will follow their parents to the communal feeding ground; areas with plentifulforage that a pigeon flock uses. Here the chicks gain their independence andintegrate into pigeon society.^[19]

Domestic pigeons were selected to breed faster than their wild ancestors;^[50] a lack of abreeding season,^[3] abundance of food in a domestic setting, and swift maturity (squabs fledge in about a month, and often have already bred and fledged a few clutches of their own before reaching a year in age) leads to swiftpopulation growth of pigeons in the flock. This fact, and the number of pigeons lost inraces or intentionallyreleased, leads to exponential growth in free-living,feral populations.^{[citation needed]}

•  
•  
  Nestlings, one day
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  Nestling, five days
•  
  Nestlings, about 10 days
•  
  18 days old
•  
  Young bird, 22 days
•  
  Feral pigeons in courtship

Pigeon breeders sometimes suffer from an ailment known asbird fancier's lung orpigeon lung. A form ofhypersensitivity pneumonitis, pigeon lung is caused by the inhalation of the avian proteins found in feathers and dung. It can sometimes be combated by wearing a filtered mask.^[51]Other pigeon related pathogens causing lung disease areChlamydophila psittaci (which causespsittacosis),Histoplasma capsulatum (which causeshistoplasmosis) andCryptococcus neoformans, which causescryptococcosis.Avian paramyxovirus is carried by pigeons and is a serious affliction in birds.^{[52][clarification needed]}

Avian mites may infest domestic pigeons and causegamasoidosis in humans. There are several methods to treat birds infested with mites or louse, including external insecticides and oral medicine.^[53]

Pigeons bred for meat are generally referred to as a meat or utility breed. The term "squab" can either refer to young birds or the meat harvested from them; these birds grow to a very large size in the nest before theyfledge and are able to fly; during this stage of development they are often fattier and seen as being tastier than the fully-flighted adults. Squabs during this stage are valued as food; inNeolithic andearly agricultural communities they were an easy and reliable source of protein, the birds requiring only reliable sources ofgrains and water (which they independently foraged for) to enter breeding condition, and the rock formations they nested in would have made forattractive dwellings for early humans.

Pigeon meat, both from squabs and from adult birds, are still a source of protein for people worldwide.^[45] Breeds of pigeons harvested for their meat during adulthood are collectively known asutility pigeons. For commercial meat production a breed of large white pigeon, theKing pigeon, has been developed by selective breeding.^[54]

Homing pigeons are a specialized type of pigeon bred for navigation and speed. Originally developed through selective breeding tocarry messages,^[55] most notablyduring warfare,^[3] members of this variety of pigeon are still being used in the sport ofpigeon racing and the ceremony of releasingwhite doves at social events.^[56]

These breeds of domestic pigeons, especially whentrained are able to return to the home loft if released at a location that they have never visited before and that may be up to 1,000 km (620 mi) away. This ability of a pigeon to return home from a foreign location necessitates two sorts of information. The first, called "map sense" is their geographic location. The second, "compass sense" is the bearing they need to fly from their new location to reach their home. Both of these senses, however, respond to a number of different cues in different situations. The most popular conception of how pigeons are able to do this is that they are able to sense theEarth's magnetic field^[b] with tiny magnetic tissues in their head (magnetoception), though the exact location of the magnetoception organ is still being researched;^[63][64] Areas of the pigeon brain that respond with increased activity to magnetic fields are the posteriorvestibular nuclei,dorsal thalamus,hippocampus, andvisual hyperpallium.^[65][66] Wherever the organ is, pigeons can detect magnetic anomalies as weak as 1.86gauss.^[67]

Another theory is that pigeons have compass sense, which uses the position of the sun, along with an internal clock, to work out direction. However, studies have shown that if magnetic disruption or clock changes disrupt these senses, the pigeon can still manage to get home. The variability in the effects of manipulations to these sense of the pigeons indicates that there is more than one cue on which navigation is based and that map sense appears to rely on a comparison of available cues.^[68]

Other potential cues used include

• The use of a sun compass^[69]
• Nocturnal navigation by stars^[70]
• Visual landmark map^[71][72]
• Navigation by infrasound map^[73]
• Polarised light compass^[74]
• Olfactory stimuli^[75][76] (see alsoolfactory navigation)

Pigeons are also kept by enthusiasts for the enjoyment ofFlying/Sporting competitions. Unlike racers, these birds are not released far from their home lofts; breeds such astipplers are bred for the ability to hover above the loft for hours at a time. Their ability to hover for a long time shows the ability of the keeper to select forendurance.^{[citation needed]}

Wild pigeons naturally flip or somersault when evading aerial predators such as large-bodiedfalcons; they are naturally selected by theextreme speeds that some stooping falcons reach (over 320 km/h (200 mph)),^[77] being able to dodge this attack at the last second.Tumbler androller pigeons are bred to enhance this ability;^[25][78] some birds have been recorded to be able tosomersault on the ground and land on its feet, and some breeds are evendeliberately bred to a point where the rolling ability is debilitative, being wholly unable to fly due to it.^[25][78]

A breed called thezurito, bred for its speed, may be used in livepigeon shooting.^[79][80]

Pigeon fanciers developed many exotic forms of pigeon through selective breeding. Perhaps the simplest form of display pigeon are those of white plumage, either trulyalbino ormerely white-feathered; these white birds were seen asholy animals or heralds of peace and are well represented in both ancient and contemporary culture.

As pigeonkeepers accrued more experience, they started selecting for increasingly more unusual features in their birds; features such as unusualplumage patterns and colors, variouscrests, foot feathering, alteredstance andproportion, or unusual behaviors are well represented in extant pigeon breeds. These birds are generally classed asfancy pigeons.

Pigeon shows are conventions where pigeon fanciers and breeders meet to compete and trade their fancy pigeons. The various pigeon breeds dubbed "American show" were developed specifically by pigeon show frequenters pursuing a certain show standard determined by theNational Pigeon Association. Fanciers compete against each other at exhibitions or shows and the different forms orbreeds are judged to astandard to decide who has the best bird.

There are many fancy or ornamental breeds of pigeons: among them are theEnglish carrier pigeons, a variety of pigeon with prominentwattles and an almost vertical stance, the Duchess breed, which has as a prominent characteristic feet that are completely covered by a sort of fan of feathers, thefantails with a fan of tail feathers like a peacock, and theVoorburg Shield Cropper which are bred to inflate their crops in an effort to woo their handlers.

• Variety of fancy pigeons
•  
  Archangel showing its extensiveiridescence
•  
  Old Dutch Capuchine
•  
  Lucerne Gold Collar
•  
  Oriental Frill
•  
  Old German Owl
•  
  Old Dutch Owl
•  
  English Owl
•  
  Chinese Owl
•  
  Valencian Figurita, one of the smallest breeds of pigeon
•  
  Portuguese tumbler, another small breed of pigeon
•  
  Old Dutch Tumbler
•  
  TheGiant Runt, one of the largest pigeon breeds
•  
  Ghent Cropper
•  
  Holle Cropper
•  
  Silesian Cropper
•  
  Voorburg Shield Cropper
•  
  Norwich Cropper
•  
  Pygmy pouter
•  
  American Show Racer
•  
  Dutch Beauty Homer
•  
  Garden or English Fantail
•  
  American Fantail
•  
  Indian Fantail
•  
  Danzig Highflyer
•  
  Oriental Roller
•  
  Birmingham Roller
•  
  Danish Tumbler
•  
  Zagreb Tumbler

Domestic pigeons aremodel organisms commonly used in laboratory experiments relating to biology; often totest medicines and chemical substances, or incognitive sciences. Research in pigeons is widespread, encompassing shape and texture perception, exemplar and prototype memory, category-based and associative concepts, and many more unlisted here (seepigeon intelligence).^{[citation needed]}

Pigeons have been trained to distinguish betweencubist andimpressionist paintings.^[81] In Project Sea Hunt, a US coast guard search and rescue project in the 1970s/1980s, pigeons were shown to be more effective than humans in spotting shipwreck victims at sea.^[82]

Pigeons are able to acquireorthographic processing skills,^[83] which form part of the ability to read, and basic numerical skills equivalent to those shown in primates.^[84]

Pigeons have notably been "employed" asmedical imaging data sorters. They have been successfully trained under research conditions to examine data on a screen for the purposes of detectingbreast cancer. They appear to use their innate visual navigation skills to do so.^[85]

Pigeons are sometimes kept as indoorpets, with the practice's popularity growing over recent years.^[86] These pet pigeons may be outfitted with "pigeon pants" (a diaper-like garment) to maintain cleanliness,^[87] and some birds may be "potty trained".^[88]

Domestic pigeons, especially theleucistic andalbinistic specimens commonly referred to as "white doves", have hada long history in symbolism.^[89]

In the United States, some pigeon keepers illegally trap and killhawks andfalcons to protect their pigeons.^[90] In theWest Midlands region of the United Kingdom pigeon fanciers have been blamed for a trap campaign to killperegrine falcons. Eight illegal spring-loaded traps were found close to peregrine nests and at least one of the birds died. The steel traps are thought to have been set as part of a "concerted campaign" to kill as many of the birds as possible in the West Midlands.^[91]

Many domestic birds have escaped or been released over the years, and have given rise to theferal pigeon.^[8] As a result of inheritedgenetic variation, feral pigeons demonstrate a wide variety of plumage patterns and colors, ranging from closely resembling wild rock doves, to patterns directly inherited from their domestic ancestors, though over time a population tends to homogenize and adopt a plumage that suits their environment, such ascamouflaging against blackasphalt, and birds that have distinct coloration from flockmates are more often targeted by predators.^[92][93] The scarcity of the pure wild species is partly due to interbreeding with feral birds. Domestic pigeons can often be distinguished from feral pigeons because they usually have a numbered metal or plasticband around one (sometimes both) legs which shows that they are registered to an owner.^[94]

Feral pigeons bear striking genetic resemblance to homing pigeons, supporting the idea that most feral pigeons trace their origins to homing pigeons who did not find their way home, or were otherwise sired by homing pigeons.^[4][8] The huge numbers of birds released inpigeon races and loft owners breaking down their lofts and leaving the pigeons to fend for themselves may be a significant factor in the persistence of urban pigeons. Ferals started to become maligned in the 1930s-40s, culminating whenNew York City parks commissioner Thomas coined the term “rats with wings” in June 1966.^[95][89]

• National Pigeon Association (USA)
• National Pigeon Association (Great Britain)Archived 28 July 2013 at theWayback Machine
• The Canadian Pigeon Fanciers Association
• Domestic Pigeons Explained (Pigeonpedia)
• Pigeonetics, a game by the University of Utah
• Pigeons Do Backflips? How Genetics Makes Them Flip!