Opposites may attract, but they don't make better parents

Researchers found birds expressing strong personality traits, such as aggressive behaviour or a willingness to explore, did a much better job of raising young if they had a like-minded partner. Where couples were markedly different in personality, chicks didn't fare as well -- being less well-fed and in poorer condition.

The research paper, published in the journal Animal Behaviour, isn't able to give a definitive reason for the parenting benefits of matched personalities -- but authors say it could be down to improved cooperation and coordination of effort.

Dr Sasha Dall, an author of the study and part of the University of Exeter's Centre for Ecology and Conservation, said: "The personality differences we focused on with these birds reflected how they go about their daily lives.

"In the case of zebra finches, to be good parents you need to be able to coordinate your behaviour so that while one parent is searching for food, the other is feeding the chick. It's a lot easier to co-ordinate your behaviour if you're similar in the way you go about things."

For the study, researchers focused in on the 'personalities' of a group of zebra finches. They were able to establish that some showed consistent patterns of behaviour, normally either reflected in different levels of aggressiveness or willingness to explore. Often the traits were combined, but some finches didn't demonstrate them at all.

Then couples were artificially paired together -- with a selection of couples who were like-minded and some who had no common traits. When mated, eggs were swapped between nests in order to distinguish the advantages of genetic, as opposed to the behavioural compatibility of parents.

Experts then studied the animals while they were feeding their chicks, and monitored the progress of hatchlings to see which couples were doing the best job as parents.

Dr Nick Royle, another author on the study, said: "We found that if birds were highly exploratory and their partners shared that trait, their offspring were in really good condition. It was the same for highly aggressive birds. If only one parent showed the trait, the chicks fared less well.

"Our study ruled out the idea that this was due to genetic compatibility, so this could only be due to the behavioural compatibility of the individuals while they were raising offspring."