The scientists suggest that having a relatively larger brain mean that these species are more adaptable to the changing conditions of city dwelling.
The "adapters" include tits, crows, nuthatches and wrens. Apparently all of the families these species come from have relatively larger brains.
Some species that do survive in cities despite having smaller brains, e.g. Swallow and Pied Wagtails, do so because they are able to find a niche that is similar to their natural habitat.
Species such as yellowhammer, reed bunting, whitethroat and pied flycatcher have comparatively smaller brains and so are less able to adapt.
According to Dr Alexei Maklakov:
The study suggests that some species and even whole families of birds are less likely to adapt to novel conditions and if we want to see them in the cities we will have to create patches of their original habitat