Birds of a feather really do flock together in much the same way as humans, scientists have learned.
Shy male great tits tend to seek the company of other birds with the same disposition, research has shown.
Similarly, introverted teenagers are likely to avoid the party crowd and keep to their own.
Researchers made the discovery after tracking thousands of birds with radio tags to map their social networks.
The study conducted in Wytham Woods, near Oxford, also found that shy birds of both sexes, while having smaller groups of "friends" than their bolder counterparts, tended to form more stable relationships.
Researcher Lucy Aplin, from Oxford University, said: "There has been a lot of work describing the range of individual personalities in the great tit. Now we are linking it to the social networks and social organisation of the species, which hasn't been done before."
The scientists recorded millions of visits made by the birds to 65 feeding stations over an entire winter to see how they interacted socially.
Birds were rated on a personality scale ranging from shy to bold, and individuals tested by introducing them to new environments.
Typically shy birds explored a strange environment very slowly, whereas bold birds carried out their recces quickly.
Birds' personalities were found to influence their social behaviour. Bolder and more outgoing birds chose quantity over quality in their relationships. They had weaker associations with more birds than shy individuals, and foraged with several different groups.
The research is due to appear in the journal Ecology Letters this week.
"Measuring the social networks we could see that bolder birds tended to hop between foraging flocks and have short-term foraging associations, while shy birds tended to maintain a foraging association over a long time," said Ms Aplin.
"Shy birds are following a social strategy where they maintain a few strong and stable social associations to minimise risk. Hopping between many flocks may increase risks for bolder birds, but might maximise rewards through improving their social position and giving them better access to information, such as the location of food."
While shy male birds tended to gravitate to similar individuals, shy females associated freely with all personalities, she said.
She added: "We think shy male birds might group together to avoid the more aggressive bold birds."
Professor Ben Sheldon, director of the Edward Grey Institute at Oxford University's Department of Zoology, said: "'By uncovering the way that different types of individuals interact non-randomly, we hope to understand how this controls the way that many processes work within populations.
"For instance, the way that information, and disease, spread in populations depends on the structure of the social network, and our work now tells us part of the reason for that structure."