For humans, it seems natural to consider what you think of your neighbors before choosing a place to live, but do animals do the same thing? According to an Oxford University study, male Parus major live up to the figurative meaning of the saying “birds of a feather, flock together,” but female birds have other priorities besides who is nesting nearby.
Parus major, commonly known as great tits – and before you start, all the jokes have been done – nest in woodlands, including England's Wytham Woods. There, PhD student Katerina Johnson established the personalities of birds caught, and then released back into the wild, by testing whether they were cautious or bold when confronted with a choice of five perches in a novel environment.
Over six breeding seasons, Johnson looked at where the birds nested to see if they were sorting themselves based on the personality traits she had measured. “We found that males, but not females, were picky about personalities, with males opting for like-minded neighbors," Johnson said in a statement. "Our results emphasize that social interactions may play a key role in animal decisions."
In Animal Behavior, Johnson concluded that decisions are made on the basis of others living nearby, rather than birds with particular personalities gravitating to parts of the woods with certain environmental conditions. “Just like students choosing their flatmates,” Johnson commented, “birds may pay more attention to who they share their living space with than simply location.”
Great tits are fiercely territorial during the breeding season, so males who are a little less aggressive struggle when surrounded by tougher neighbors, and apparently seek a quieter life elsewhere. On the other hand, bolder birds may find that it is worth putting up with equally aggressive neighbors if they fight off predators.
Although it remains to be seen whether the work is applicable to many species, it breaks new ground because, as the paper notes, “few studies have investigated the significance of the social context of animal personalities, and such research has largely focused on the social organization of non-territorial populations.”
High schools provide plenty of examples of the way humans sort themselves by personality, but animals can provide a simpler model to study the evolutionary benefits of this behavior, and whether it can explain the maintenance of personality differences in populations.
IFLScience has covered Johnson's work before, in the form of her evidence that friendship networks act as better painkillers than morphine. It's not unusual for scientists to cover very diverse topics in the course of their careers, but to range across such different areas of science while working on a PhD is unusual. Johnson told IFLScience: “The underpinning link is my interest in personality and social behavior (both its causes and consequences) in humans and other animals.”