How feeding birds may be polluting local environments, spreading diseases and damaging the eco systems

Feeding birds have a religious significance in some places. 

People offering grains to feral Common Pigeons (Columba livia) at designated kabutarkhanas or illegitimate feeding places are a common sight these days in our cities. It may seem to be a noble deed and is also perceived to be so by many. Hundreds of pigeon-lovers are seen flocking around the grain sellers to purchase the grains to be fed to the pigeons. Mostly such feeding stations are adjacent to places of worship. There are many people who have created mini feeding stations in the balconies, on the window ledges or terraces. 

A large number of people feed pigeons for religious reasons, thinking that by feeding pigeons they are helping the birds and perhaps this helps in washing away their sins. People also believe that feeding pigeons brings prosperity to those who feed them.

There are others who feed pigeons thinking that pigeons are hungry, need food and would not survive unless fed by them. Grains are purchased and literally scattered in heaps for the pigeons to feed. Such artificial feeding has led to overpopulation of pigeons that is much beyond the carrying capacity of any place.

Supplementary feeding of ring-necked pheasants (Phasianus colchicus) has a major impact on local nutrient cycles in the United Kingdom. Credit: John Harding/British Trust for Ornithology

What keeps the populations of bird species in the wild balanced, be it a pigeon or an eagle? Food chain, to a great extent, regulates relative abundance of each species based on their reproduction, deaths and predator-prey relationship. In case of feral pigeons in cities across India, there is a problem of plenty. In the wild, the Common Pigeon (previously known as the Blue Rock Pigeon) is seen around cliffs and rocky areas, which they prefer for nesting. However, in cities and towns their preference for naturally occurring cliffs has been replaced by parapets, windows, balconies, AC compressor units and any such flat surface in city buildings where pigeons seek shelter. Due to the constant availability of food, pigeons have started nesting throughout the year; unlike in the wild where nesting season coincides with the food availability in nature. Predatory birds help in keeping the population of pigeons in control by feeding on them in the wild. But unfortunately urbanisation has practically wiped out the predatory birds from most city limits.

Had it been not for our compassionate feeding, the pigeons would have survived anyway but in lesser numbers, enough to be sustained on the natural food availability in and around the cities. By providing them with ready food, pigeons in cities have lost their natural ability to scavenge and survive on their own. Scavenging for food is an important exercise for wild birds that they must indulge in. Such ‘compassionate’ feeding may attract birds (and also rodents like rats and mice) close to you but may also result in nutritional deficiencies in birds. Let the birds decide what they wish to feed on instead of us deciding what they should feed on!  

The population explosion of pigeons in cities and towns is a serious trend that is slated to grow in future as there is no dearth of food offered to them and nesting sites in cities. Lots of pigeons around may make some people happy but doctors and veterinarians have often expressed concerns over this issue and advise refraining from feeding pigeons.

Keeping leftover food or other food stuff in the balcony for other species of 'hungry' birds should also be reassessed and probably discouraged. Veterinarians warn that such bird feeders may act as a nodal point of disease spread to other species of birds for emerging diseases of infectious nature such as bird flu.

As the faecal matter gets dried up it forms fomites which could travel in air facilitating spread of infection. Symptoms of coughing, rhinitis, arthritis and headache could easily be encountered. Recently the husband of an actress died because of an infection he contacted from his pet pigeons. People in the vicinity of pigeons and their droppings are at the highest risk of catching infection. Other species of birds are at great risk of mutually getting infected as well and it would make the infection to persist for longer.

On the other hand, birds quickly get used to our food, which obviously is not their natural food. Also, birds not feeding naturally might affect the ecological food chain as they may not eat the fruit which only germinates when it passes through that bird's intestine. Our ignorance in these matters can have serious consequences that we may not be even aware of. Then why should we interfere with their routine of scavenging for food? The natural balance of wildlife populations is very sensitive, and we must be careful of how our interactions affect them, say the experts.

Don’t get discouraged as a bird lover! You certainly have a role to play as there are many ways of helping in the conservation of birds. Misplaced compassion is not conservation and often does not help. Planting, nurturing and protecting plant species that provide shade, perches, nesting places, fruits and flowers for wild birds is a more sustainable and a logical way to help in bird conservation than artificially feeding wild birds. There are several other ways of getting involved in the conservation of birds. But of course, it requires you to move out of the comfort of your homes and venture out into the wilderness.

As long-term measures, getting involved in wildlife conservation agencies in personal capacity as volunteers, supporting the community at the fringe of protected areas and organising nature clubs and awareness trails on bird conservation for students, are options which you could consider to make an impact on overall bird conservation.

An appeal to the concerned authorities and people to take note of the potential health hazards and ecological ramifications associated with feral pigeons and take immediate steps to close down the kabutarkhanas and other pigeon feeding stations. The surplus population of feral pigeons will thus move out elsewhere in the quest for food. Use of some anti-fertility drug or some such means to control the population growth among the pigeons without harming them could also be an option to be considered in controlling the growing pigeon populations.

People from all communities should come together to sensitively address this problem. 

I myself tried several times to educate people on this but they were unable to come out of their religious sentiments. 

Now new research  by  scientists shows that backyard bird feeders, although put out with the best of intentions, is changing the chemistry of local ecosystems, including introducing a potentially harmful amount of phosphorus into the environment.

The study, published Aug. 7 in Frontiers in Ecology and the Environment, shows that, collectively, the millions of household bird feeders throughout the world add up to a large transfer of additional nutrients into local environments. This artificial supplementing of a natural process may lead to unanticipated ecological impacts.

The seeds, nuts and grains provided for birds are rich with fats and proteins. Yet most of this nutrient-rich bird food is sourced on the global market and transported thousands of kilometers to feeder stations.

Birds are incredibly effective dispersers. They eat a lot, fly a lot and poop a lot. This means that extra nutrients provided at feeders eventually make their way into local ecosystems.

In their research, which examined the United Kingdom as a case study,  researchers found that the scale of phosphorus supply in supplementary foods provided for garden and game birds equalled about 2.4 Gg/year.

While phosphorus is an essential element for both plants and animals, too much of it can cause problems. Concerningly, phosphorus release by bird feeding was comparable to other human activities, such as industrial waste and sewage misconnects, which are considered environmental polluters.

The greatest supply of extra nutrients was provided for game birds. The researchers found that each year, more than twice as much phosphorus was provided to pheasants, partridges and other game birds compared to garden birds.

This supplementary food constitutes a significant component of game bird nutritional intake and helps elevate densities beyond the natural carrying capacity. While this may benefit land owners in the short-term, it could spell ecological trouble in the long-term.

When additional nutrients from bird feeding enter natural environments, they have profound consequences for the species that live there, if bird feeding occurs at high rates or over long periods of time, it can begin to change the fertility of the landscape, upsetting the balance of the ecosystem.

Eventually, the nutrients in bird feed are washed into rivers, where they may also exacerbate issues of eutrophication, that is, they may produce too many rich nutrients, causing algae to grow too densely and harming animals that live in or near the rivers.

Does this mean bird feeders are bad? It's not that simple, the researchers say. The bigger question is, how do different factors interact to change the environment.

It is important to study animal dispersal of nutrients, because in some places, animals can spread important nutrients in a way that benefits ecosystems, but in other cases, like in the case of bird feeding, they may spread too many nutrients, causing problems.

We must continually re-evaluate bird feeding practices as new evidence arises. Previous research has already shown that bird feeding is linked to changes in bird community composition, behaviour, distribution and transfer of avian disease.

This study suggests that the impact of garden feeding is significantly less than that of gamebird feeding when it comes to nutrient dispersal, the findings add a new dimension to our efforts to understand the balance of costs and benefits of putting out food in our gardens.

Pigeons tend to breed and roost in groups. The biggest problem they cause is the amount of feces (droppings) they produce. The build-up of pigeon feces on buildings and other structures is visually unappealing and is made worse by the fact that pigeon droppings are acidic and erode metal and stonework.

Pigeon droppings harbour  fungi that could lead to hardening of lung tissues in humans and controlling the infection in the birds will help in reducing the incidence of lung diseases. 

More importantly, pigeon droppings may pose a health hazard to the general public. Pigeons have been associated with a variety of diseases, including histoplasmosis and cryptococcosis.

Histoplasmosis is a disease caused by a fungus that grows in pigeon droppings. The fungus can also be found in bat droppings or in the soil, and is carried by the wind. When removing droppings, people may breathe in some of the fungus. When exposure is high, the fungus can cause infection.

Symptoms of histoplasmosis begin to appear about 10 days after initial infection and can include fatigue, fever, and chest pains. Most infections have no symptoms or appear as a mild respiratory illness. People with weakened immune systems (like cancer patients or people living with HIV/AIDS) are generally more at risk of developing histoplasmosis. The disease cannot be transmitted from person to person.

Cryptococcosis is another fungal disease related to pigeon droppings and grows in soils throughout the world. It is very unlikely that healthy people will become infected even at high levels of exposure. A major risk factor for infection is a compromised immune system.

Exposure to pigeon dropping is the cause for developing pneumonia in certain cases in India according to health experts.

Although avian influenza (bird flu) viruses are less common in birds more closely associated with human environments such as domestic chickens, turkeys, pheasants, pigeons and parrots, we still have to be careful.

So it is not advisable to have pigeon nests in human dwellings.

Sources: 

Andrew J Abraham et al, Supplementary bird feeding as an overlooked contribution to local phosphorus cycles, Frontiers in Ecology and the Environment (2024). DOI: 10.1002/fee.2793

https://kkartlab.in/group/some-science/forum/topics/2816864:Topic:1...

https://www.dnaindia.com/analysis/standpoint-how-feeding-pigeons-in....

https://www.sciencedirect.com/topics/agricultural-and-biological-sc...