Feral pigeons (Columba livia domestica), also called city doves, city pigeons, or street pigeons, are pigeons that are derived from the domestic pigeons that have returned to the wild. The domestic pigeon was originally bred from the wild rock dove, which naturally inhabits sea-cliffs and mountains. Rock (i.e., "wild"), domestic, and feral pigeons are all the same species and will readily interbreed. Feral pigeons find the ledges of buildings to be a substitute for sea cliffs, have become adapted to urban life, and are abundant in towns and cities throughout much of the world. Due to their abilities to create large amounts of excrement and to carry disease, combined with crop and property damage, pigeons are largely considered a nuisance and an invasive species, with steps being taken in many municipalities to lower their numbers or completely eradicate them.
|Columba livia domestica|
|Feeding in a park|
|Scientific classification |
C. l. domestica
|Columba livia domestica|
Feral pigeons are essentially the same size and shape as the original wild rock dove, but often display far greater variation in colour and pattern compared to their wild ancestors. The blue-barred pattern which the original wild rock dove displays is generally less common in more urban areas. Urban pigeons tend to have darker plumage than those in more rural areas.
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 coloration 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 coloration in domesticated birds than in their wild relations. Eumelanin generally causes grey or black colouration, while pheomelanin results in a reddish-brown colour. Other shades of brown may be produced through different combinations and concentrations of the two colours. As in other animals, white pigeons have little to no pigment.
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.
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. Due to their ability to produce crop milk, pigeons can breed at any time of year.
Courtship rituals can be observed in urban parks at any time of the year. The male on the ground or rooftops puffs up the feathers on his neck to appear larger and thereby impress or attract attention. He approaches the hen at a rapid walking pace while emitting repetitive quiet notes, often bowing and turning as he comes closer.
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.
Abandoned buildings are favorite nesting areas. Mass nesting is common as pigeons are a community flocking bird; often, dozens of birds share a building. Loose tiles and broken windows provide access, and pigeons are adept at spotting new access points, for example following property damage caused by strong winds.
Nests and droppings tend to stay clustered and remain dry when out of the weather. Pigeons are particularly fond of roof spaces. These often contain water tanks. Any water tank or cistern on a roof must, therefore, be secured and sealed off to keep the pigeons out of them. The popularity of a nesting area does not seem to be affected by the pigeons' population density.
On undamaged property, the gutters, window air conditioners and empty air conditioner containers, chimney pots, and external ledges are used as nesting sites. Many building owners try to limit roosting by using bird control spikes and netting to cover ledges and potential nesting places on buildings. This has little effect on the size of the pigeon population, but it can reduce the accumulation of droppings on and around a particular building location.
In the UK, only the larger and more wary common wood pigeon, which often shares the same territory and food supply, builds nests in trees, usually close to roads.
In Wendell Levi's The Pigeon, he describes the crowing/cooing of pigeons as mostly being associated with strutting and fighting in male birds. Hens also coo, but this is noticeably less guttural than the cooing of the cock. Cooing is also more frequent between couples during mating and nesting.
Both parents participate in the incubation of the eggs.
Pigeons breed when the food supply is abundant enough to support embryonic egg development, which in cities, can be any time of the year. Laying of eggs can take place up to six times per year.
Pigeons are often found in pairs during the breeding season, but usually the pigeons are gregarious, living in flocks of 50 to 500 birds (dependent on the food supply).
Feral pigeons can be seen eating grass seeds and berries in parks and gardens in the spring, but plentiful sources exist throughout the year from scavenging (e.g., remnants left inside of dropped fast-food cartons) and they also take insects and spiders. Additional food is also usually available from waste bins, tourists or residents who feed birdseeds to pigeons for reasons such as: empathy, fun, tradition and as means for social interaction . Pigeons tend to congregate in large, often thick flocks when feeding on discarded food, and have been observed flying skillfully around trees, buildings, telephone poles, and cables, and even through moving traffic just to reach a food source.
In the UK, pigeons are covered under the "General Licences" and can be humanely culled by the land owner or their agent for a variety of reasons (mainly crop protection). It is illegal to kill/destroy nests for any reason other than those listed under the general licences.
In the United States, the Migratory Bird Treaty Act of 1918, which protects native birds, does not apply to feral pigeons, starlings, or English sparrows, because they are introduced species. It is usually legal to kill feral pigeons in the U.S. Methods such as poisons may be regulated, however.
City squares famous for pigeons
Many city squares have large pigeon populations, such as Washington Square Park in New York City, George Square in Glasgow, the Piazza San Marco in Venice, Dam Square in Amsterdam, The Gateway of India and Kabutarkhana in Mumbai and (prior to 2000) Trafalgar Square in London.
Feral pigeons often only have small populations within cities. For example, the breeding population of feral pigeons in Sheffield, England, has been estimated at only 12,130 individuals. Despite this, feral pigeons usually reach their highest densities in the central portions of cities, so they are frequently encountered by people, which may lead to conflict.
Feral pigeons are widely considered pests, and are known to act as reservoirs and vectors of multiple human and livestock diseases. It is rare that a pigeon will transmit a disease to humans due to their immune system.
Research into whether pigeons play a part in spreading bird flu have shown pigeons do not carry the deadly H5N1 strain. Three studies have been done since the late 1990s by the US Agriculture Department's Southeast Poultry Research Laboratory in Athens, Georgia, according to the center's director, David Swayne. The lab has been working on bird flu since the 1970s. In one experiment, researchers squirted into pigeons' mouths liquid drops that contained the highly pathogenic H5N1 virus from a Hong Kong sample. The birds received 100 to 1,000 times the concentration that wild birds would encounter in nature. "We couldn't infect the pigeons," Swayne said. "So that's good news."
However, other contagion besides bird flu are transmitted by pigeons. For example, the bacteria Chlamydophila psittaci is endemic among pigeons and causes psittacosis in humans. It is generally transmitted from handling pigeons or their droppings (more commonly the latter). Psittacosis is a serious disease but rarely fatal (less than 1%). Pigeons are also important vectors for different species of the bacteria Salmonella, which causes diseases as salmonellosis and paratyphoid fever. They are also known to host avian mites, which can infest human habitation and bite humans, a condition known as gamasoidosis.
There is ample reason for the concerns of pigeons damaging property, due to their size and proximity to people and their dwellings. Pigeons often cause significant pollution with their droppings, though there is little evidence of them driving out other bird species. Pigeons are labeled an invasive species in North America by the USDA.
Long-term reduction of feral pigeon populations can be achieved by restricting food supply, which in turn involves legislation and litter (garbage) control. Some cities have deliberately established favorable nesting places for pigeons—nesting places that can easily be reached by city workers who regularly remove eggs, thereby limiting their reproductive success. In addition, pigeon populations may be reduced by bird control systems that successfully reduce nesting sites.
Peregrine falcons, which are also originally cliff dwellers, have also adapted to the skyscrapers of large cities and often feed exclusively on rock pigeons. Some cities actively encourage this through falcon breeding programs. Projects include Unibase Falcon Project and the Victorian Peregrine Project.
Other predators of the pigeon have been recorded, including sparrowhawks, crows and seagulls. Great white pelicans have also been recorded killing and consuming pigeons in St. James's Park, despite alternative food sources being available.
Larger birds of prey occasionally take advantage of this population as well. In New York City, the abundance of pigeons (and other small animals) has created such a conducive environment for predators that the red-tailed hawk has begun to return in very small numbers, including the notable Pale Male.
Due to their non-selective nature, most avian poisons have been banned. In the United States market, only 4-aminopyridine (Avitrol) and DRC-1339 remain registered by EPA. DRC-1339 is limited to USDA use only, while 4-AP is a restricted-use pesticide, for use only by licensed applicators.
The use of poisons has been proven to be fairly ineffective, however, as pigeons can breed very quickly, and their numbers are determined by how much food is available; that is, they breed more often when more food is provided to them. When pigeons are poisoned, surviving birds do not leave the area. On the contrary, they are left with more food per bird than before. This attracts pigeons from outside areas as well as encouraging more breeding, and populations are re-established quickly. An additional problem with poisoning is that it also kills pigeon predators. Due to this, in cities with peregrine falcon programs it is typically illegal to poison pigeons.
Reducing food supply
A more effective tactic to reduce the number of feral pigeons is deprivation. Cities around the world have discovered that not feeding their local birds results in a steady population decrease in only a few years. As scavengers, pigeons will still pick at garbage bags containing discarded food or at leftovers carelessly dropped on the ground, but securely disposing of foodstuffs will greatly reduce scavenger populations. Feeding of pigeons is banned in parts of Venice, Italy.
In 1998, in response to conservation groups and the public interest, the National Wildlife Research Center (NWRC), a USDA/APHIS laboratory in Fort Collins, Colorado, started work on nicarbazin, a promising compound for avian contraception. Originally developed for use in resident Canada geese, nicarbazin was introduced for use as a contraceptive for feral pigeons in 2007.
The active ingredient, nicarbazin, interferes with the viability of eggs by binding the ZP-3 sperm receptor site in the egg. This unique contraceptive action is non-hormonal and fully reversible.
Registered by the EPA as a pesticide (EPA Reg. No. 80224-1), "OvoControl P", brand of nicarbazin, is increasingly used in urban areas and industrial sites to control pigeon populations. Declared safe and humane, the new technology is environmentally benign and does not represent a secondary toxicity hazard to raptors or scavengers.
Avian contraception has the support of a range of animal welfare groups including the Humane Society of the United States (HSUS), the American Society for the Prevention of Cruelty to Animals (ASPCA) and People for the Ethical Treatment of Animals (PETA). Avian contraceptives are also perceived by civilans as an acceptable method for population control, over other methods such as prohibition to feeding or extermination.
Dummy egg nesting
When eggs are removed in artificial pigeon houses, the interval between reproductive attempts is strongly reduced, which reduces the efficiency of the method. Dummy egg nesting programs have therefore been tested in some cities with mixed results. There, the eggs are removed and replaced with dummy eggs. The real eggs are then destroyed. One such structure, in Batman Park in Melbourne Australia, was unsuccessful in attracting pigeons and has since been removed. "Melbourne City Council's $70,000 pigeon loft turned into scrap metal" Park The loft used in Melbourne is on stilts, with a cage door allowing access from beneath for accessing the structure at night when the pigeons are asleep.
Monitoring dove population
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Estimating the population size of pigeons, is necessary for monitoring and control programs of pigeons in parks and other urban areas. The methods used for estimating populations sizes are:
- Stratified grids: This method consists in dividing the area where pigeons occur in 500x500m squares. 34% of the squares are selected randomly and pigeons are counted in a 5 meters radius for 5 minutes.
- Point-counts: standing in the center of a park, the observer makes a 360 degree turn while counting individuals with a manual mechanical counter in a radius of approximately 50m, limited by the streets and buildings that surround the park.
- Panoramas: taking 360 panoramic photographs, while standing at the center of the park, and using a software to place a number above the counted pigeon in the panoramic photograph. This method has been proved as the most effective of all.
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- Doves as symbols – appearing, usually white in color, in many settings as symbols of love, peace or as messengers, in the symbolism of various religions and of both military and pacifist groups
- Squab – a young pigeon, typically under four weeks old, or its meat
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