Crows: They're just like us. They love fast food, but fast food doesn't always love them back.

Urbanized crows survive on a diet that's mostly human leftovers. Oftentimes, it's fast food. Think pizza crusts, bread crumbs and other processed foods that don't occur naturally in nature. To see what kind of effect that diet was having on the birds' health, a team of ornithologists at Hamilton College in Clinton, New York, led a study to test the effect of cheeseburgers on urban crows' cholesterol levels.

Previous studies had shown that wildlife in urban areas, such as house sparrows, had high cholesterol levels. The scientists began by testing 140 crow nestlings in Davis, California, in a region that spanned rural to urban. And indeed, they found the more urban the bird, the higher its cholesterol.

Their next study took place in rural Clinton, New York, but this time, they supplemented the birds' diets with a high-cholesterol food: cheeseburgers. At one point, they were calling in 100 McDonald's cheeseburgers at a time. "They thought we were joking," Andrea Townsend, the lead researcher, told National Geographic.

Just like humans, crows should practice moderation when it comes to fast food. PierreSelim [CC by SA 3.0]/Wikimedia Commons

Notably, the cholesterol levels did not have an impact on the birds' survival. And the baby crows who received a burger-rich diet ended up, technically, in "better body condition" than their rural counterparts. Although "if you’re a chubby crow, essentially, that’s considered to be good condition,” Townsend noted.

The study, published in the scientific journal The Condor, believes that crows might develop heart disease later in life, but more research is needed.

For now, just like us, the birds would do better eating cheeseburgers in moderation. If you want to continue feeding the birds in your neighborhood, the scientists suggest something less processed, and as close to natural as you can get.