Effects of assortative mating for personality on reproductive success in greylag geese, Anser anser

Consistent behavioural responses of individuals (i.e. personality) have been linked with reproductive output and success across a range of taxa. In species with biparental care, the behavioural compatibility of breeding partners may also affect reproductive output, perhaps because it allows greater pair coordination during breeding attempts. The aim of this study was to investigate whether pairs of greylag geese are assortatively paired for personality, and whether these traits within pairs affect reproductive output. We used repeated behavioural assays in the field to quantify three personality traits: activity (focal observations), boldness (flight initiation distance) and aggressiveness (response to mirror image). We assessed their correlation with three measures of reproductive output (clutch size, hatching success and fledging success). All three personality traits were significantly repeatable; however, we found no evidence that pairs within the flock routinely assortatively paired for any trait, regardless of the pair bond duration. Nevertheless, there may still be fitness benefits associated with pair compatibility. Pairs in which the partners were similar in average boldness had higher hatching success, although this trend was not found for clutch size or fledging success. These results suggest that the benefits of having similar predator defence strategies within pairs differ across the breeding cycle, resulting in no overall selection for assortative mating for boldness.