If you’ve walked around a city with pigeons, you might have noticed that many of them are missing toes or have deformed feet. These foot deformities are common and may arise due to a number of different ailments including: chemicals that make surfaces sticky or apply an unpleasant odor; physical deterrents that are placed on buildings in an attempt to prevent pigeons from landing or nesting in an area; a Staphylococcus bacteria that causes ‘bumblefoot’; or physical objects (string, synthetic hair, etc.) that get wrapped around toes.
A team in France led by Frédéric Jiguet sought to understand how local environmental conditions predict toe and foot mutilations in pigeons on the streets of Paris. To do this, they sampled 46 areas throughout Paris, walking the area for a maximum of one hour, until they sighted 30 pigeons.
For each pigeon, they recorded the total number of damaged/missing toes, the age of the pigeon, and the pigeon’s color. They included color because color has been correlated with endoparasites (parasites inside the body), such that darker individuals have a lower endoparasite number and greater immune response (Jacquin et al. 2011). The researchers collected repeated samples in five locations to ensure that mutilation rates collected in the hour-long sampling period were representative of the population and did not vary with time.
To understand how pigeon foot deformation correlated with the environment, the team also collected information about landcover, human population density, foot traffic, number of hours per week that street markets were open (to help understand if pigeons were attracted to an area because of food), the density of household waste, the density of hair salons, and air quality.
What did they find?
The researchers first looked for correlations in their data and found that human population density and the density of household waste were strongly correlated. The authors also found correlations between human population density, foot traffic, and the density of hairdresser shops.
In relation to toe mutilations, there was no correlation with pigeon color, meaning that the greater immune response seen in darker pigeons may not be enough to combat necrosis, and mutilations were equally likely to occur on either foot. As expected, adult pigeons were more likely to have mutilated toes than juveniles.
When it comes to environmental factors, the authors found that noise pollution and air pollution were the most likely factors in their model to predict the occurrence of toe mutilations. Human population density was the most likely predictor of the number of mutilated toes. The authors stated that toe mutilation “tended to increase with the density of hairdressers” however, they did not find that the density of hairdressers was statistically significant in any of their models. Moreover, the authors found that human population density and the density of hairdresser shops were correlated, therefore the increase in toe mutilations in areas with more hair salons may be due to the correlation between human population density and hair salons.
Despite the findings of the study, the media has published dozens of articles about how human hair (a byproduct of hairdressers) is causing toe mutilations, but there are basic questions that, we as scientists, should start to ask before we jump to the conclusion that hairdressers are leading to pigeon toe mutilations. We need to ask: is there strong evidence in the study, and does that “headline” in the media make sense biologically?
What should we learn from this?
First, stop and think before you tweet (I admit to not always following this rule). I became aware of this article because all of a sudden people were tagging me in tweets about how human hair causes foot deformities in pigeons. It makes sense, I’m studying pigeons and I’m thankful that I have a community that helps me keep up on new research.
However, having plenty of experience catching pigeons and removing string from their feet, this article immediately jumped out to me as odd. What I usually remove from pigeon feet isn’t natural hair. Most often I find either string or synthetic hair (like the kind used in wigs or weaves). I assume most natural hair breaks far too easily or deteriorates too quickly to get wrapped around pigeon feet. Even without my experience, there are a few other alarm bells that go off:
- The number of hair salons in a neighborhood is correlated with population density so even though toe mutilation “tended to increase with the density of hairdressers” the most reasonable explanation for this is because neighborhoods with more people have both more pigeon toe mutilations and more hair salons. This does not mean that more hair salons leads to more pigeon toe mutilations, but instead that greater population density leads to more pigeon toe mutilations.
- Beauty salons often offer other services (e.g. eyebrow threading) which may be more likely to cause foot entanglements because of the materials of threading tools (i.e., synthetics)
- The hair that is cut off at hair salons (usually) isn’t long enough to get entangled around pigeon toes. Most people go in for a trim and have a few centimeters removed — which isn’t nearly long enough to get wrapped around and entangle pigeon feet.
Second, the statistics do not support the idea that hair salons lead to pigeons with more toe mutilations. While the authors did find that pigeon toe mutilations increased in areas with more hair salons this relationship was not included in their final model and is likely the result of higher human population density leading to an increase in the number of hair salons.
What should you do if you find a pigeon with an injured foot?
Finally, if you see a pigeon with an injured foot, and you’re able to capture it, you can bring it to a local wildlife rehabber. For a list of wildlife rehabbers in the United States, click here. For wildlife rehabbers in Canada, click here. In other parts of the world, contact your local government, who should be able to point to you appropriate care.
Read the full paper here:
Featured photo credit:
“Walking Tall” by Tom Raftery is licensed under CC BY-NC-SA 2.0
Thank you to Kaylee Byers who encouraged me to write this post and provided valuable feedback before publication.
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