Aug. 26 (UPI) -- Birds that adapt to life among humans often pick up the eating habits of their bipedal neighbors, picking at discarded pizza slices and tossed-out cheeseburgers. According to a new study, the shift in dietary habits comes with a change in cholesterol levels.
American crows living in urban settings, researchers recently found, have higher blood cholesterol levels than their rural peers.
For the study, published this week in the journal The Condor: Ornithological Applications, scientists measured the blood cholesterol levels of 140 crow nestlings living along an urban-to-rural gradient in California. Researchers also supplied rural nestlings in New York with McDonald's cheeseburgers.
Like the city-bred crows tested in California, the New York nestlings developed higher cholesterol levels than their fast food-free peers.
Though urban birds didn't live as long as their rural peers, on average, cholesterol wasn't to blame.
"Despite all the bad press that it gets, cholesterol has benefits and serves a lot of essential functions," study author Andrea Townsend, a researcher at Hamilton College in New York, said in a news release. "It's an important part of our cell membranes and a component of some crucial hormones. We know that excessive cholesterol causes disease in humans, but we don't know what level would be excessive in a wild bird."
Still, researchers don't recommend providing birds with fast food.
"Wild birds haven't evolved to eat processed food, and it might have negative consequences that we didn't measure, or that will only show up over longer periods of time," Townsend said. "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. 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."
Previous studies have shown birds living in the cities are angrier and more aggressive than their peers from the country. In backyards, research suggests the introduction of bird feeders can create unique hierarchies among wild birds.