>From an article in gizmodo published yesterday:


https://gizmodo.com/crows-get-higher-cholesterol-from-eating-our-cheeseburg-1837587414

"City living is producing something new for you to worry about: high
crow-lesterol (sorry, I'm sorry, I'm trying to delete it).

"Crows generally aren't picky eaters, and primarily survive on plants,
carrion, and food scavenged from human-produced sources like landfills and
garbage cans. But the food we throw away might not be as healthy for these
scavengers as the food they'd find in a people-free environment. Scientists
wondered whether crow diets were suffering from urban living. So,
naturally, they fed the corvids some McDonald's cheeseburgers and then
analyzed their blood.

Cholesterol is an important molecule for bodily function, but too much has
been linked to disease in humans. What too much cholesterol does to other
animals, scientists aren't sure of. A team led by assistant professor
Andrea K. Townsend at Hamilton College in New York set out to measure the
effects of urbanization and a low-quality diet on crows' cholesterol levels
and overall survival.

The researchers banded and took blood samples from 140 crow nestlings in
Davis, California, and 86 crow nestlings in the Clinton, New York, and
monitored them for either two or three years. For some of the crow families
in New York, the researchers supplemented their diet by placing a
McDonald's cheeseburger within 33 feet of their nest, five to six days a
week.

Urban environments (which the researchers defined as environments with more
impervious surfaces) seemed to be associated with higher cholesterol
levels, as well as decreased survival. And the fledgelings of the
burger-fed birds seemed to have higher cholesterol, on average, than those
that didn't receive burgers.

But it's unclear whether cholesterol itself was a good or bad thing for the
birds, and the burger-fed birds seemed to be in better condition than the
birds who didn't receive McDonalds. It's also unclear what constitutes
"high cholesterol" for a crow. However, it is clear that urbanization
overall seemed to have a negative effect on crow survival for the first
three years of life, according to the paper
<https://academic.oup.com/condor/article/121/3/duz040/5536814>
published in *The
Condor: Ornithological Applications.* The results seem to match those of
other experiments on house sparrows, Northern Bahamian rock iguanas, and
San Joaquin kit foxes, in which urban populations (or populations in area
with more humans) are found to have higher cholesterol.

There are still plenty of questions left unanswered by a study like this.
The researchers only monitored the young crows for two to three years-;what
about the effects of a fast-food diet on older crows? The researchers
concluded that they'd need to observe crows for longer in order to fully
understand any possible ill effects that higher cholesterol might have.

This all goes to show that city living doesn't just change humans-;it
changes the animals in our urban habitats, too."
--
Nadine
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