City birds have bigger brains and more sex than country cousins

BIRDS that live in the city are smarter than their countryside counterparts because they have more sex and are forced to use their brains more, scientists have found.

To survive in the unnatural environment of busy cities, birds have developed bigger brains and produce more offspring. Previous research found that birds with larger brains had advantages such as finding new food sources and avoiding human-made hazards.

However, scientists have now found that some smaller-brained birds cope well in an urban environment due to high numbers of breeding attempts.

Dr Ferran Sayol, the study’s lead author, of the University of Gothenburg,

Sweden, said: “Cities are harsh environments for most species and therefore often support much lower biodiversity than natural environments. The species that can tolerate cities are important because they are the ones that most humans will have contact with in their daily lives, and they can have important effects on the urban environment within our cities.”

Researchers analysed databases and collections containing brain and body size, maximum lifespans, global distribution and breeding frequency. They contained details on more than 629 birds in 27 cities around the world and showed brain size played a vital role. But it was not the only path to success.

“We identified two distinct ways for bird species to become urban dwellers,” explained Dr Sayol. “On the one hand, species with large brains, like crows or gulls, are common in cities because large brain size helps them deal with the challenges of a novel environment. On the other hand, we found small-brained species, like pigeons, can be highly successful if they have a high number of breeding attempts over their lifetimes.”

The study suggested the two strategies represented distinct ways of coping with urban environments.

When considering the impacts of our increasingly urban future on our wildlife neighbours, it will be important to consider reproduction and brain size, researchers said.

The findings are published in Frontiers in Ecology and Evolution.