Boldness, mate choice and reproductive success in Rissa tridactyla

As many long-lived seabirds are biparental and monogamous, individuals need to choose their mates wisely. While assortative mating based on physical traits is widely studied, mate choice in sexually monomorphic species based on behavioural traits remains poorly understood. We propose that personality is a possible factor on which mate choice is based and that certain personality traits within a behavioural syndrome confer a greater fitness. Here we measure boldness, a commonly explored behavioural syndrome, in black-legged kittiwakes, Rissa tridactyla , nesting at Middleton Island, Alaska, U.S.A. We measured boldness by presenting subjects with a novel object and recording the response. We considered the first principal component scores from the analysis of these responses to represent an individual's boldness. Some kittiwakes exhibited the strategy of assortative mating based on boldness, and bold birds that mated assortatively exhibited the greatest reproductive success. Within a breeding season, individuals became bolder as they reached the most critical point in the breeding season (chick hatching), which supports our finding that bolder individuals have greater reproductive success. We conclude that personality should be considered when investigating mate choice because individual personality may have an important influence on reproductive success.