The importance of mate behavioural compatibility in parenting and reproductive success by cockatiels, Nymphicus hollandicus

In species with long-term pair relationships, behavioural compatibility between mates could be a significant source of selection among pairs. We explored the relation between behavioural compatibility and reproductive success in cockatiels, a socially monogamous species with biparental care and variable compatibility. The mate behavioural compatibility measure, derived from our previous work with these birds, was based on five pair-level variables: proximity, behavioural synchrony, copulation, allopreening responsiveness and total aggression. We operationally defined mates as more compatible when they showed greater proximity, synchrony, allopreening responsiveness and copulation frequencies and lower frequencies of aggression. Using a captive, seminatural population, we tested the following three interrelated hypotheses: (1) pairs with greater behavioural compatibility before breeding should have greater reproductive success; (2) among pairs that laid fertile eggs, pairs with greater behavioural compatibility should show better incubation coordination and (3) pairs with better incubation coordination should hatch more fertile eggs. Our results were consistent with these hypotheses. Pairs that laid eggs had significantly higher behavioural compatibility scores than did those that laid no eggs. Pairs with higher behavioural compatibility scores reared significantly more chicks to independence even after controlling for the effects of pair bond duration and parental age. Among pairs that laid fertile eggs, mates with higher behavioural compatibility scores had greater incubation coordination, measured by periods during which only one parent at a time attended the eggs, and greater hatching success of fertile eggs. Behavioural compatibility between mates in socially monogamous species may have reproductive consequences, and emergent behavioural features of pair relationships may have evolutionary significance. (c) 2005 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.