Individual Behavioral Responses to Novel Stimuli in Breeding Common Terns (Sterna hirundo)

Abstract

The way individuals respond to novel stimuli may provide insight into their ability to thrive in different situations, or into their role, for example during reproduction. Here, we analyze variation in the behavioral response of common terns (Sterna hirundo) when confronted with such novel stimuli. We quantify the latency to return to the nest upon facing a novel stimulus, and test for short-term repeatability, whether variation in this trait is explained by sex, age, and reproductive phase, and whether there is evidence for assortative mating with respect to this trait. We find a repeatability of 32% across the responses recorded during incubation and chick-rearing. Moreover, females take a longer time to return to the nest than males, and this latency is longer during incubation than during early chick rearing. Variation in this trait is not related to age, and responses are not correlated between the two members of a breeding pair. We suggest the sex effect reflects role differences during parental care, while the vulnerability of the offspring may dictate the effect of reproductive phase. Finally, we assess exploratory behavior during the incubation phase, and find that it does not vary with sex, age, or the response to the novel stimulus. Further work should assess the long-term repeatability of the two traits we assessed, as well as elucidate whether connections to other repeatable behaviors observed in these birds exist.