Feeling tired? Blame city living: Living in urban areas could have major impact on biological clocks of humans and animals, say researchers

Researchers compared the internal rhythms of blackbirds living in the countryside and in urban areas and found they differ significantly

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The Independent Online

Living in urban areas could have major impact on the biological clocks of humans and animals, a study suggests.

City life can be a draining experience compared to living in the countryside. Now scientists have proven its not just humans who are affected.

A team of Scottish scientists measured the circadian rhythms, the 24-hour cycle of biological activity, of blackbirds living in the countryside and in urban areas and found they differ significantly.

The researchers say these changes to their biological rhythms could lead to more health problems and shorter lives. The study also found that city living makes us active for longer and less rested.

The blackbirds in the city began their days earlier and ended them later, being active for around 40 minutes longer than the rural blackbirds. The internal clocks of the city-dwelling birds were “less robust” and more prone to disturbance, the researchers said.

The differences in urban birds may have developed in response to artificial light and increased noise, they said.

Adult male European blackbirds were captured from Munich and a nearby rural forest. They fitted each one with a lightweight radio-transmitter which monitored their daily activity in the wild for 10 days before the birds were recaptured.

They were then kept in light-proofed, sound-insulated chambers and their circadian rhythms were measured under constant conditions. Once the tests were complete, the birds were returned to the wild.

The study, which has been published in the journal Proceedings of the Royal Society B, was carried out by Glasgow University and the Max Planck Institute for Ornithology in Germany.

Barbara Helm, from Glasgow University's Institute of Biodiversity, Animal Health and Comparative Medicine, said: “The daily cycles of activity and rest are based on biological rhythms which have evolved as an adaptation to the rising and setting of the sun.

“We found that the rhythms of urban birds in the wild differ significantly from their forest counterparts.

“On average, they began their daily activities around 30 minutes before dawn, while forest birds began their day as the sun rose. The city birds ended their days around nine minutes later, meaning they were active for about 40 minutes longer each day.

“In constant laboratory conditions, urban birds' circadian (daily) rhythms were clearly altered, running faster by 50 minutes than forest birds and being clearly less robust. There seems to be a different beat to city life.

“Our work shows for the first time that when sharing human habitats, a wild animal species has a different internal clock.

“We'd be keen to find out the costs and benefits of modifying biological rhythms in blackbirds and other animals commonly found in our cities. This may help us to better understand the challenges of coping with urban life.”