Being friendly but not too friendly helps sparrows breed successfully

(Image: Pixabay CC0) - A new study shows that sparrows with more opposite-sex friends contribute more to the gene pool, but 'average' friendliness wins out in the long term. Scientists have assumed for a long time that traits associated with how social an animal is - such as shyness or extraversion - have a genetic basis. This means some traits should be 'selected for' - they should be passed down by animals that are more successful at breeding as a result of their sociality. We find that birds with an average amount of 'friends' have better fitness than those at the extremes. Jamie Dunning But this has been difficult to test in the real world. Now, a team led by Imperial College London researchers have conducted a huge genetic study using the sparrow population of the island of Lundy. The study, published today in Behavioural Ecology , shows sparrows that have more opposite-sex friends outside the breeding season are more successful at passing on their genes during the subsequent breeding season.