The trash-heavy diets of crows living in crowded cities may be giving the birds high cholesterol.
Hamilton College assistant professor of Biology Andrea Townsend and several colleagues studied the cholesterol levels of crows living in urban environments and published the results on Monday in the science journal, The Condor: Ornithological Applications.
The researchers conducted tests on 140 crows living in urban and rural areas around Davis, California, and fed a control group of New York crows McDonald cheeseburgers to determine how much fast food affects birds’ cholesterol levels.
The team established that crows living off a steady diet of fast food did have higher cholesterol, and found that the California crows tended to have higher cholesterol when living in more urban areas. The effects of higher cholesterol on birds are less clear.
While birds living in urban areas had a higher mortality rate, the scientists found that birds with easy access to discarded human food were healthier.
“Elevated cholesterol levels could indicate access to high-calorie, high-fat anthropogenic foods, which might, in some contexts, improve body condition, potentially offsetting other negative effects of urbanization,” the study says.
Although urban crows have higher cholesterol, the scientists are unsure of whether the cholesterol levels are too high.
“We know that excessive cholesterol causes disease in humans, but we don’t know what level would be ‘excessive’ in a wild bird,” Townsend said.
Townsend recommends for people not to feed local wildlife because the science is still unclear.
“Feeding wild birds can be a great way to connect with nature, and it can be a refreshing change to think that we’re doing something that helps animals out,” Townsend said. “At the same time, though, I do worry that some of the foods that humans give to wild animals, and living in an urban environment in general, might not be good for their health.”
