Evidence for personality development: juvenile red knots vary more in diet and exploratory behaviour than adults

Evidence is accumulating that foraging behaviour and diet link to personality traits, yet little is known about how these associations emerge during development. It is expected that behaviour becomes more consistent with age, and thus experience. We compared exploratory behaviour and diet variances of juvenile and adult red knots shortly after migration to intertidal mudflats from tundra breeding grounds. By identifying the timing of the switch from tundra to marine isotopic signatures, we were also able to ask whether juveniles that arrived earlier were more consistent in exploration behaviour. We found that juveniles had a more diverse diet than adults, and that juveniles were less repeatable in exploration than adults. While juveniles had larger within-individual variance, among-individual variance was similar between age groups. Juveniles that arrived earlier did not vary more in exploratory behaviour compared to those that arrived later, suggesting that consistency in exploration was developed over a longer period than the four weeks of our study. Our findings suggests that after initial exploration of a novel habitat, juveniles likely try-out foraging techniques which later develop into consistent behaviours that differ among individuals. This study illuminates how personality can develop with experience in a free-living animal.