Crows and humans have much in common besides the whole bird and the mammal. Like us, these clever Korvids have an excellent memory and a penchant for puzzles. They can make and use tools and move around the world in complex social groups. They are even a bit monogamous – just like us.
Well, the less enjoyable news: Crows are also junk foods – and their bodies are not immune to their effects. In a study published today in the journal The Condor: Ornithological Applications scientists found that urban crows tend to have higher cholesterol levels than their rural relatives. The culprit seems to be the human-like diet, which also includes the fatty, high-calorie McDonald's cheeseburgers who frequent many urban lanes.
However, this fat spit is not necessarily alarming and does not exist. However, there is evidence that elevated cholesterol has a long-term impact on the crows' health. However, the crows incident has always been complex, as these birds are among the few species that actually thrive in urban environments. In the United States, the American crow (Corvus brachyrhynchos)] effectively commands a range from coast to coast, in part due to the bold combination of mental sharpness and apparent steel stomach. While crows in the countryside often eat fruits, nuts, insects, and small mammals, these opportunistic omnivores eat just about anything they can get their beaks into, including uplifted garbage.
In a Lot In some cases, this indiscriminate food is practical: food is food, whether served on a silver platter or fished out of the mud at the bottom of a dumpster. But modern human nutrition ̵
Researchers have known for years that people in urban areas tend to have higher cholesterol levels than rural areas. Study author Andrea Townsend, a behavioral biologist at Hamilton College, was not particularly surprised when an analysis of 140 American crow crows from Davis, California, showed the same pattern Super Size Me with a new crows cohort in New York State. During the incubation periods of 2017 and 2018, Townsend and her colleagues threw their days throwing cheeseburgers within sight of well-known crow's nests – a bait that invariably awoke the interest of the parent birds and brought back the greasy treats to their cubs.
The experiment required a steady supply of fast food, and the team became regulars at the McDonalds in Clinton Village, where often about 100 burgers were ordered at a time. "We got a lot of looks of shock and horror from the staff," says Townsend. (The crows, on the other hand, were "enthusiastic about the entire study design.")
After a few weeks on the cheeseburger diet, nestlings had more cholesterol in their blood than young birds who had not been fed extra food. Crows only stay in the nest until they are about one month old. Afterwards they will be harder to catch, according to Townsend. For this reason, it is unclear whether these particular birds had higher cholesterol levels or had any negative effects in the long term.
The fast food correction may even have helped the birds: Before the cheeseburger nestlings flew In the stable they were bigger and heavier. In the Crow community, it's actually good to be "chubby" as a child, Townsend says, and burly chicks tend to be healthier as adults.
This result seemed to be supported by another team's nestling had studied in California. During the two or three years after these crows were fully grown, the researchers examined them to see if higher cholesterol at a young age was affecting their survival. Contrary to Townsend's expectations, this was not the case: crows from across the cholesterol spectrum seemed to be about the same.
The reasons are not very clear. But while there is a clear limit to the "desirable" level of cholesterol in humans, there is no such statistic for our feathered friends – and a higher cholesterol level in youth does not necessarily mean a high Cholesterol in adulthood.
In other words, crows can easily use the molecule. Despite its poor reputation in nutritional circles, cholesterol is indispensable for the life of the animals and forms an important structural component of the cells. It is important enough that our livers use it regularly – and unusually low levels of cholesterol in humans can cause their own health problems.
So when it comes to the health of birds and cholesterol, there is no easy answer to that point, "says Anne Clark, an ecologist and crows expert at Binghamton University who was not involved in the study. But, she adds, maybe that's to be expected. "The relationships between humans, food and urban animals are certainly complicated, just as it is complicated in today's world to feed well."
It should not be the lack of negative effects on these birds. This is an invitation to throw caution (or cheeseburgers) aside, says Townsend. The study only tracked their feathered subjects for a few years – but crows can live in the wild for more than 15 years and in captivity for more than 50 years. Had the cheeseburger intervention or follow-up been longer, things might have looked different, she says.
These results may not necessarily apply to other species. Sparrows, foxes, iguanas, and turtles also appear to be cholesterol driven through urban environments, but the ultimate consequences of these changes are largely unclear. According to Corina Newsome, a wildlife biologist and conservation ecologist at Georgia Southern University who was not involved in the study, crows are among the creatures best suited for tasting occasional burgers. However, this is not the case for all animals – or even for all birds – she says.
Given the impact of total urbanization on animal welfare, it is becoming even more complex, says Animal Welfare Officer J. Drew Lanham and Ornithologist at Clemson University, who was not involved in the study. While Townsend's team found no link between cholesterol levels and crow mortality, there was a worrying trend: the more urban a bird's habitat was, the less likely it was to survive.
"There is something going on in the urban environment. Whether mental or physiological, that affects your well-being, "says Lanham. "I wonder about things like stress … and what an urban environment means to the mind and body."
These ongoing insecurities are perhaps more than enough reason to keep wildlife, Newsome says, especially when it comes to nutrition. After all, "If it's not healthy for us, it's probably not healthy for them."