I’ve gotten the occasional concerned comment about the perceived negative effects of wild bird feeding. In an attempt to understand the benefits and unintended consequences of feeding wild birds, I’ve put together this blog post with some of the latest research in this area. I spent hours reading ornithology journals to report back that little is known about the long-term effects of feeding wild birds. That doesn’t change the fact that there are people who will argue fiercely for and against feeding birds.
Wild Bird Feeding Concerns
First, let’s go over the concerns of feeding wild birds. There are many. These include that birds will become dependent on provided food sources, feeder crowding will spread avian diseases, food provided lacks adequate nutrition, negative effects on biodiversity, and population increases in unpopular species. Let’s take a closer look at each of these:
The idea that feeding wild birds leads to dependency is common. It’s believed that if you start and stop feeding wild birds, the birds will suffer and die because their food source will be gone. There has only been one study done on this and it found no evidence of dependency among winter-fed black-capped chickadees. Surprisingly, the study found that almost 80% of chickadees’ diets were naturally derived even though they had easy-access to feeders.
Another study coming out of Australia tracked the eating habits of magpies. Magpies are the most common bird species found at feeding stations in Australia. The research found that “natural foods dominated the diets of both fed and unfed magpies, making up 76% and 92% of all items consumed respectively…Both fed and unfed magpie parents provisioned their chicks predominantly with natural food. Magpies were not reliant or dependent on supplementary food provided by wildlife feeders at any time during the breeding season. Although many magpies did utilize suburban feeding stations extensively, they continued to forage for and provision their chicks with natural food.”
These two studies suggest that dependency is not straightforward and that some bird species regulate their intake of supplementary foods.
Spreading Avian Disease
Birds frequenting feeding stations come into close contact with one another. This close contact has led people to fear the spread of avian diseases. In fact, there have been several studies that prove that avian diseases have spread with the use of bird feeders. It is unclear, however, if the rate of disease actually increases from feeder visitations.
For example, a study published by PlosOne showed that bird feeders “may not necessarily increase the rate of disease” in house finches. This was also observed with the common greenfinch and common chaffinch. This study led some scientists to conclude that “although there is no doubt that infections are more likely owing to the cramming of birds at feeding stations, the highly gregarious social
Lack of Adequate Nutrition
Another concern is that people are providing wild birds with food that does not contain the adequate nutrients that they need to survive. Some of the most common foods fed to birds are bread and seed. I have found no studies that talk about their long-term effect on birds. If we extrapolate from the study on black-capped chickadees and Australian magpies, we might conclude that this isn’t a big deal because these birds are relying primarily on naturally-derived food sources. We need more research to understand the effect on nutrition and bird feeding.
We do know that multiple studies have demonstrated that supplementary feeding “profoundly influence reproductive outcomes” of targetted species. Jones and Reynolds explain, “the majority of these studies show that increasing the available food resource advances the onset of reproduction, prolongs the breeding period and increases the number of young produced per year…In some bird species, more food also results in more offspring per breeding attempt.” Similarly, an article in the Journal Emu-Austral Ornithology argues, “we can now be reasonably certain about some important likely outcomes of feeding. First, wintering birds supplied with additional foods have greatly enhanced survival, and second, food supplementation almost always advances the key reproduction dates: laying, hatching, fledging and, often, re-nesting. Thus, supplemented birds typically breed earlier and more often.”
Negative Effects on Biodiversity
There are also concerns that when we feed wild birds, we help the survival of introduced species to the detriment of local species. Jones and Reynolds explain, “this is…a key concern in Australia, where the predominance of large and aggressive species such as pied currawongs at feeding stations has been implicated in the local decline of numerous smaller and more subordinate species.” However, as Jones notes in another paper, given the studies that demonstrate wild birds are not dependent on supplementary foods, the connection is difficult to establish between lack of biodiversity and bird feeding.
Increase in Unpopular Species
Finally, people worry that feeding birds will increase unpopular species like mice. Bird feeders attract mice and other rodents. They eat the seeds discarded by birds.
Benefits to Feeding Wild Birds
As I mentioned earlier, wintering birds have a greater chance of survival when we feed them. Feeding birds also benefits their reproduction. But, there are two benefits of feeding wild birds that I haven’t addressed yet. The first is the increased ability of scientists to monitor birds with citizen science partnerships. The second is the benefit that people get when interacting with birds. Let’s take a closer look at both:
Citizen Science Partnerships
People who feed birds often watch their
Two examples of citizen science projects are Project FeederWatch in the US and Garden BirdWatch in the UK. This type of research is invaluable to scientists. Jones argues, “the scale, detail, and coverage” of citizen science partnerships “could never be replicated by even the most organized research group. The many bird
Positive Effects on People
There have been some recent studies that talk about the effects of wild bird feeding on us! An article published by Cox and Gaston found that “people who fed birds regularly felt more relaxed and connected to nature when they watched garden birds.” They also observed that “feeding birds may be an expression of a wider orientation towards nature.”
Similarly, a study published by the University of California Press argued that “promoting interaction with garden birds might also lead to increased human engagement with nature and potential for a positive effect on quality of life, particularly within urban environments, where arguably such engagement is most needed.”
In yet another article, O’Leary and Jones conclude that bird feeding is “worthy of a far greater level of attention for the fundamental reason that it is one of the principal forms of human-wildlife interaction in the contemporary world. For increasing numbers of urban dwellers, the main venue of any interaction with wild animals will be with the birds they encounter within the suburban environments in which they live.” This is the case here in Ottawa where people gather to feed the chickadees and nuthatches every weekend. This
More Research Needed
It’s clear that more research is needed on the long-term effects of feeding wild birds. For now, based on this evidence, I’m going to continue feeding local birds and take precautions to minimize the associated risks. This includes, not feeding birds processed foods like bread and regularly cleaning bird feeders to help reduce the risk of spreading avian diseases.
I encourage you to do your own research on this subject. If you find any scientific articles that I missed, please feel free to include them in the comments section. I’m going to continue researching this subject.
Robinson, Lawson, Toms, Peck, Kirkwood, Chantrey, Clatworthy, Evans, Hughes, Hutchinson, John, Pennycott, Perkins, Rowley, Simpson, Tyler, and Cunningham. 2010. “Emerging Infectious Disease Leads to Rapid Population Declines of Common British Birds” in PlosOne.