Pathway 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. Behaviour is expected to become more consistent with age and with foraging experience. We compared exploratory behaviour and diet variances of juvenile and adult red knots, Calidris canutus islandica, shortly after migration to marine intertidal mudflats from terrestrial tundra breeding grounds. By identifying the timing of the switch from terrestrial to marine isotopic signatures, we were also able to ask whether juveniles that arrived earlier, and thus had longer experiences in a particular environment (nonbreeding grounds), were more consistent in exploration behaviour. We found that juveniles had a more diverse diet and were less repeatable in their exploratory behaviour than adults. This change in repeatability was largely driven by greater within-individual behavioural variance in the juveniles compared to the adults. The amount of time juveniles experienced in a marine environment did not affect the variation in their exploratory behaviour, suggesting that consistency in exploration was developed over a longer period than the 4 weeks of our study. Our findings suggest that after initial exploration of a novel habitat, juveniles likely try out foraging techniques which later develop into consistent behaviours that differ between individuals. This study illuminates how personality can develop with experience in a free-living animal.