Turns out fast food hits crows the same way as it does humans: In the cholesterol levels.
Scientists measured the cholesterol levels of crows in different parts of the country — and found that the more urbanized the area, the higher the cholesterol in the crows.
Why? Probably because the crows are eating the scraps from our terrible, tasty processed food. To test whether fast food could actually be the culprit, the scientists ran an experiment, leaving McDonald's cheeseburgers near the nests of crows in the rural area of Clinton, NY. Sure enough, the cholesterol levels of those rural crows shot upwards.
But wait, what about the ethics of intentionally raising the cholesterol levels of crows? It's not so big a deal for them, necessarily. Higher cholesterol correlates with better health in some animals, so it's okay for crows to supersize it, apparently?
She and her team found that while urban crows had lower survival rates overall, the cholesterol didn't seem to hurt the crows, and even boosted the body condition of the nestlings, leaving them a little plumper.
Still, Townsend doesn't recommend flinging burgers to birds at the park. "We know that excessive cholesterol causes disease in humans, but we don't know what level would be 'excessive' in a wild bird," says Townsend. "It is also possible that, if elevated cholesterol does have negative effects, they would show up later. In humans, it can take many years for excessive cholesterol to lead to disease."
Jukka Jokimäki at the University of Lapland in Finland was surprised the fast food didn't have a bigger negative influence on the birds' health. "There are probably some other urban-related factors that are more important for the crows," says Jokimäki, adding that other aspects of city life may tax crows' health, such as car collisions and disease.
The original paper, unpaywalled, is here, and it quite fun to read. Check out this data on crow cholesterol levels …
(CC-2.0-licensed photo of a crow courtesy the Flickr feed of Valters Krontals)