It really is true: Birds of a feather do flock together.

Shy male birds prefer the company of fellow introverts, according to a study published this week in Ecology Letters.

Researchers associated with the Edward Grey Institute of Field Ornithology at the University of Oxford in England studied great tits (Parus major) in Wytham Woods, near Oxford, to determine how personality affects social behavior.

Previous research found evidence that birds with larger social networks can find more food, with the advantage going to individuals more apt to mingle.

The intersection of personality and social behavior is a new and growing area of study in biology and behavioral ecology, says study co-author Julie Morand-Ferron. "If you take the simple definition of personality as behaving consistently over time, then you can find personality traits in vertebrates and insects and all sorts of animals."

For the purposes of this study, shy or "reactive" birds are slower to explore and less likely to take risks. Bold or "proactive" birds prefer high risks and high rewards.

Personality Tests

But researchers first needed to determine which great tits were shy, and which were bold explorers.

So they captured 221 great tits from the wild and released them one by one into a room containing five artificial trees. The scientists then recorded their movements.

"The very shy birds basically don't move that much," says Morand-Ferron. "They seem to be very careful. They hop from tree to tree, or they fly a bit."

Bolder birds, on the other hand, "have a very high activity rate. They land on the ground. They fly quickly."

With the personalities of the 221 captured birds established, the researchers released them back into the wild, where they tracked the birds' movements.

Shy Guys

The great tits of Wytham Woods have been studied for more than six decades, and most of them wear plastic rings containing transponders around their legs. Sensors on the 65 feeding stations dotting the forest pick up the transponder signals whenever the birds come close enough.

Over the winter months, when great tits congregate in loose flocks, the researchers monitored where the tested birds were feeding and who they were hanging out with.

They discovered that male birds who exhibited shy behavior in captivity tended to stay in flocks with their shy friends in the wild for longer periods of time, while the bolder birds flitted from flock to flock.

In a previous paper, Morand-Ferron and her colleagues determined that birds with larger social networks—like those bold birds—find out about hidden sources of food quickly because they have access to more information.

But they're not sure yet what evolutionary advantage shy males might gain from sticking together. In the paper, the authors hypothesize that the shy males are trying to avoid the more aggressive bold males, but Morand-Ferron emphasizes that this is a question for further study.

No word yet on whether a bird in the hand has been proved to be worth two in the bush.