The Urban Environment Is Stressing Some Birds to Death

Urban spaces can be a boon to wildlife. Thanks to the heat-island effect, they’re often warmer than the woods. And human garbage makes for easy eatin’, as anybody who’s seen a pigeon plumped into a feathery balloon from stale hot-dog buns knows.

But there’s also evidence cities harm animals—artificial lights can addle entire ecosystems, for example, and glass architecture kills millions of migrating birds each year. Now researchers in Sweden are spreading the dismal word that by simply being born in cities, certain kinds of birds are doomed to a heightened risk of premature death.

Pablo Salmón at Lund University and others wanted to see if Parus Major, aka the great tit, fared any differently whether it grew up in a city or rural environment. So they took bird siblings and had one group reared in the countryside and the other in Malmö, then tested their blood about two weeks later for changes to the animals’ telomeres.

A telomere is a string of DNA dangling from the end of a chromosome that’s a “suggested biomarker of longevity,” write the researchers. Blood sampling revealed the urban birds had shorter telomeres compared to their rural kin. Here’s more from a university press release:

According to the researchers, the induced stress that the urban great tits are experiencing is what results in shorter telomeres and thereby increases their risk of dying young….

“Although there are advantages to living in cities, such as the access to food, they seem to be outweighed by the disadvantages, such as stress—at least in terms of how quickly the cells of the great tits age,” says biologist Pablo Salmón who conducts research in the field of evolutionary ecology at the Faculty of Science, Lund University.

The scientists say they were “surprised” to find this ostensibly irreversible change had occurred in such a short time. The next step might be to test other creatures for telomere abnormalities, Salmón adds, as these “results also raise questions concerning the aging of other animals affected by urbanization, and humans for that matter.”