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This is Scientific American 60 Second Science. I'm Suzanne Bard.

As long as humans have been building cities,

wildlife has been fleeing from them.

After all, cities are noisy, crowded, and dangerous for animals, including many birds.

But we know that some birds do very well in urban areas.

So in many cities we have pigeons or dogs,

any kind of crowd species.

University of Gothenburg biologist for Ron Sayall.

He and his colleagues are interested in why some birds thrive in urban environments.

They suspected that having a large brain in relation to overall body size could be an advantage.

Having a big brain give you more behavioral flexibility.

So for instance in cities, maybe these big brain species are better able to identify opportunities for finding

food, also to identify dangers in the city.

But this scenario doesn't account for birds like pigeons, which are decidedly lacking in the brain power department.

Sial and his colleagues analyze the relative brain sizes of 629 bird species from 27 cities around the world as well as their

tolerance for urban life. They found that birds that flourish in cities come into

extremes. They're either big-brained but

produce few offspring over their lifetime or their small-brained and super-fertile.

So then this means that we have these two opposing strategies.

...