The researchers placed the male Great Tits in a new habitat and noted how they responded. The bolder birds were naturally keen to investigate the new surroundings but shy birds were nervous and unsure.
It would seem that males, not females, were choosy about different characters, with the males deciding on like-minded neighbours.
Aggression peaks in male birds during the breeding season when they are safeguarding their territory, which may explain the reason for the changes in behaviour. Timid birds may choose to avoid building a nest near to bold males to reduce the competition for females.
For a stronger, courageous bird, having the same dynamic neighbour, may also gain the benefit of effectively keeping intruders at bay.
Why not study your own garden bird visitors? Watched over a period of time you should be able to make out a pecking order.
This could translate to humans as well and explain why evolution has given us different personalities making us choose who we prefer to have as our friends.