While living in urban areas, there is noticeably more trash and garbage lying around than in rural areas. Many species of birds in urban areas have found lots of processed food to eat, which is mostly not apart of their diet. This causes concern for their health. Andrea Townsend, an ornithologist at Hamilton College in Clinton, New York, led a study with her team to show how urban living affects the health of American crows. The second part of the study examined what happened to rural crow populations when they were fed everyone's favorite food, cheeseburgers.
The team tested 140 crow nestlings (both rural and urban) in Davis, California, which is an urban area. They researched them over a span of three years. To no surprise, they found that more urbanized crows have higher cholesterol. Next, they tested the rural crows in Clinton, New York by giving each crow three McDonald's cheeseburgers a day. They then compared the cholesterol levels of these crows to crows that are urban but not fed cheeseburgers. The team found that cholesterol levels did not have an effect on the birds' survival.
According to Townsend, regardless of their cholesterol levels, urban birds did have lower survival rates than rural birds. This is mostly likely due to higher chances of car collisions, disease, predators, and poor food quality. Furthermore, she notes that cheeseburger-fed rural crows obviously weighed more in size than rural birds not fed cheeseburgers. Townsend also mentions that crows can live more than 15 years in the wild, and those with higher cholesterol might develop diseases in the future.
So, regardless of the cholesterol levels in cheeseburger-fed crows versus those not fed cheeseburgers, it did not have an effect on the birds' survival in the short-term. More studies would need to be done long-term to determine if these birds develop cholesterol-related diseases later on in their lives.