Predators (
Larus michahellis) eating a feral pigeon it has killed in
Naples, Italy
Peregrine falcons
Falco peregrinus, which are also originally cliff dwellers, have also adapted to the skyscrapers of large cities and often feed exclusively on feral pigeons. Some cities actively encourage this through falcon breeding programs. Projects include the Unibase Falcon Project and the Victorian Peregrine Project. Other species of
falcons have also been observed to hunt down ferals. Other predators of the pigeon have been recorded, including
Eurasian sparrowhawks (
Accipiter nisus),
crows (
Corvus spp.), and large
gulls (
Larus spp.). Larger birds of prey occasionally take advantage of these pigeons as well.
Goshawks have been known to specialize on feral pigeons even outside of urban settings. In New York City, the abundance of feral 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. Other common predators of feral pigeons in North America are
raccoons,
opossums,
great horned owls, and
eastern screech owls. The birds that prey on pigeons in North America can range in size from
American kestrels to
golden eagles. In London, the population of
great white pelicans at
St. James's Park has also been recorded killing and consuming pigeons even when alternative food sources are available. In cities in Western Europe,
European herring gulls may occasionally hunt and consume feral pigeons in addition to other birds and small mammals. Despite their importance in the diet of urban predatory birds, feral pigeons are known to transmit several diseases to their consumers, as they may be
reservoirs of several avian diseases, often
subclinically.
Raptors may contract
West Nile Virus through consumption of infected bird species, such as
crows,
house sparrows, and pigeons.
Trichomoniasis, frounce, or canker is a significant disease in raptors both captive and wild-living. Symptoms include
caseous plaques in and around the
oropharynx, and lesions may be found in the
lungs,
air sacs,
sinuses,
ear canal and kidneys. Trich has been found to be
resistant to several drug treatments, and it is thought that "
preventive treatments" that use insufficient dosages may be one of the causes. These diseases may prove to be fatal to the raptors;
Columbid Herpesvirus-1 has a near 100% mortality rate in raptors.
Artificial control Deterrence methods include
bird spikes and the recently introduced optical gel deterrent.
Food supply reduction 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. 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 favourable nesting places for pigeons, nesting places that can easily be reached by city workers who regularly remove eggs, thereby limiting their reproductive success. 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, the
American Society for the Prevention of Cruelty to Animals and
People for the Ethical Treatment of Animals. Avian contraceptives are also perceived by some civilians as an acceptable method for population control, over other methods such as prohibition to feeding or extermination.
Dummy egg nesting ,
Melbourne. Designed specifically to encourage nesting and allow removal of fertilised eggs to prevent population growth, it was a landmark in its own right before its removal, for lack of success, around 2015. 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. The loft used in Melbourne was on stilts, with a cage door allowing access from beneath for accessing the structure at night when the pigeons are asleep.
Poison 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. == Monitoring pigeon population ==