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Pigeons may be proxies for pollution in people

Pigeons, surrounded by snow, cluster on dry ground around a New York City storm drain to stay warm
Pigeons of New York. Photo: Cem Ozdel / Anadolu Agency / Getty Images

Pigeons and people living in the same neighborhood are likely to have comparable rates of lead exposure, according to a study presented at the 2018 meeting of the American Association for the Advancement of Sciences in Austin, Texas.

Why it matters: The birds might one day serve as the metaphorical canary in a coal mine, alerting officials to pollution-caused illnesses before they occur in humans.

Pigeons have been used to look for the presence of environmental contaminants for some time. But until now, researchers didn’t know if their toxin levels correlated with those in humans in the same area.

What they did: Rebecca Calisi-Rodriguez, a biologist at the University of California, Davis, and undergraduate student Fayme Cai analyzed blood samples from 825 sick or injured birds brought to a wildlife rehabilitation center in New York between 2010-2015, and looked at the zip code they were found in. New York requires that young children be tested for lead exposure each year, so the scientists then cross-referenced public records of those results with those of the pigeons.

Why they did it: Although lead has been banned in the United States for decades, its residue can still be found in gasoline, pipes and paint that can be sources of dangerous levels of exposure. Researchers already knew that pigeons picked up environmental toxins, but until now no one knew if pollution in pigeons corresponded with pollution in people. Pigeons live their entire lives within a very small (about 2 kilometer) radius so if they test positive for toxins, they were probably exposed locally.

What they found: New York City neighborhoods with higher rates of high blood lead levels in children also had the highest rates of blood lead levels in pigeons. The association was strong, which means testing pigeons for pollutants could be a good proxy for testing people.

“Why test pigeons when you can test people?” is one of the most common questions Calisi-Rodriguez gets, especially since New York City requires mandatory lead checks for children.

  • Because pigeons live outside and eat off the ground, they might have greater exposure to environmental toxins than people. That means it could be easier to find those toxins in pigeon.
  • Other cities don’t have mandatory blood-lead level testing.
  • Drawing blood from humans (particularly children) can be traumatic for the patient.
  • Taking blood from humans in a region requires jumping through more hoops and possibly costs more than taking blood from pigeons.

What’s new? In a collaboration with Matthew Macmanes at the University of New Hampshire, Rodriguez-Calisi found that when pigeons are stressed (by being placed in a pillow case), different genes are activated in both male and female pigeons. Rodriguez-Calisi wonders if male and female pigeons (and possibly people) might respond to a chemical stressor, like lead, differently. Their initial study did not take the sex of pigeons into account but hope to in future work.

What’s next: Rodriguez-Calisi would also like to study populations of pigeons in other parts of the country to see if toxins vary in urban/rural areas and use the pigeons as indicators of other pollutants.