Feral pigeon
[4] Many domestic birds have gotten lost, escaped or been released over the years, and these gave rise to populations of feral pigeons.
Their domestic ancestry predisposed them to living near humans, and they subsequently became adapted to urban life, being abundant in towns and cities throughout much of the world.
Several authorities, including municipalities consider them to be pests and an invasive species, often disparagingly referred to as "rats with wings".
[14] Local selective pressures have been suggested to explain the geographical variation across feral pigeons in the United States.
[15] The blue-barred pattern which the original wild rock dove displays is generally less common in more urban areas.
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.
[18] The avoidance of mating between related individuals is ordinarily regarded as adaptive since it decreases the likelihood of inbreeding depression in progeny that can be caused by the expression of deleterious recessive alleles.
[19] However in feral pigeons it was found that despite detectable inbreeding depression, pairwise relatedness between mates was significantly greater than it was between nonmates.
[19] This suggests that mating with close kin provides inclusive fitness benefits that outweigh the costs of inbreeding depression.
[19] Studies of feral pigeons in a semi-rural part of Kansas found that their diet includes the following: 92% maize, 3.2% oats, 3.7% cherry, along with small amounts of knotweed, elm, poison ivy and barley.
Bird feeders, often tourists or residents who feed pigeons, do so for reasons such as empathy, fun, tradition and as a means for social interaction.
The hippoboscid fly Pseudolynchia canariensis is a typical blood-sucking ectoparasite of pigeons in tropical and subtropical regions.
[32] Other studies have presented evidence of clinical signs and neurological lesions resulting from infection but found that the pigeons did not transmit the disease to poultry reared in direct contact with them.
[35] Three studies since the late 1990s were performed by the US Agriculture Department's Southeast Poultry Research Laboratory in Athens, Georgia, according to the center's director, David Swayne.
In one experiment, researchers squirted into pigeons' mouths liquid drops that contained the highly pathogenic H5N1 virus from a Hong Kong sample.
[27] Pigeons are not a major concern in the spread of West Nile virus: though they can contract it, they apparently do not transmit it to humans.
[41] 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.
Healthy, well-fed pigeons excrete feces that are composed largely of a brown to greenish-brown mass with a white cap; the white cap is composed of uric acid crystals, with some of the uric acid dissolved within urea that comprises the liquid urine, which is transparent and often absorbed by the mass of solid waste of the feces, which maintains its shape when the bird is in good health.
The color of the resultant fecal matter is helpful in diagnosing the condition of the bird; droppings which appear dull yellow is indicative of starvation especially if watery, green may be a sign of liver disease due to an abundance of excreted biliverdin, bright green being an abundance of passed bile implying bowel problems or not having eaten recently, and red-brown showing kidney disease.
[55] Peregrine falcons, which are also originally cliff dwellers, have also adapted to the skyscrapers of large cities and often feed exclusively on rock doves.
[66][67] In cities in Western Europe, European herring gulls may occasionally hunt and consume feral pigeons in addition to other birds and small mammals.
Raptors may contract West Nile Virus through consumption of infected bird species, such as crows, house sparrows, and pigeons.
Symptoms include caseous plaques in and around the oropharynx, and lesions may be found in the lungs, air sacs, sinuses, ear canal and kidneys.
[75] Long-term reduction of feral pigeon populations can be achieved by restricting food supply, which in turn involves legislation and litter (garbage) control.
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.
Declared safe and humane, the new technology is environmentally benign[78] and does not represent a secondary toxicity hazard to raptors or scavengers.
