City Birds Have Shorter Telomeres

Great Tit. Victor Tyakht/Shutterstock

Telomeres are the little protective DNA “caps” at the ends of chromosomes, and telomere length has been linked to lifespan, aging, and cancer. According to a new Biology Letters study, growing up in urban environments shortens the telomere lengths of songbirds.

Living in urban areas has its pros and cons. There’s more air, light, and noise pollution, but there’s often more opportunities. For wildlife, that includes cozier temperatures, nooks and crannies for breeding, and a cornucopia of human food (though this is typically lower quality than natural food). Lots of studies have found that early-life conditions have lifelong implications, but less is known about development in urban environments.


To study the impacts of city life on wildlife, a team led by Lund University’s Pablo Salmón conducted a “cross-fostering” experiment using urban and rural nestlings of great tits (Parus major) living in southern Sweden. They placed two-day-old city-born chicks into the nest boxes of country parents and country chicks into the care of city parents. The team weighed and measured the chicks when they were 15 days old, and a 100-microliter blood sample was taken in order to measure the lengths of their telomeres. Because telomeres shorten each time the cell divides, telomere length is thought to be an indicator of longevity. In wild populations, telomere length correlates with both lifespan and survival.

The team found that great tits raised in the city had shorter telomeres, and it doesn’t matter where they were born. Overall, telomere length differed by 10.7 percent between the habitats: Urban nestlings raised in the country had 11 percent longer telomeres than their non-fostered siblings, while rural nestlings reared in the city had 10.4 percent shorter telomeres than their non-fostered siblings.

This is the first study to show that growing up in an urban environment shortens telomere length. For developing birds at least, city living for a period as brief as just two weeks imposes challenges – such as stress, pollution, and differences in diet – that come with potentially irreversible effects.


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