Exploration speed in Red Knots affects spring migration timing, but only after experimentally constrained fuelling conditions

Individual variation in avian migration timing is still poorly understood, yet recent evidence shows that it is closely linked to personality traits and may also be affected by food availability. Here, we examined how the interaction of the personality trait exploration speed and food availability affected the departure timing of Red Knots Calidris canutus from their wintering grounds. Using experimental manipulations of food access and measures of exploration speed in captivity followed by tracking of released individuals, we show that fast‐exploring birds departed later but only when subjected to restricted food access in the experiment, whereas birds with unlimited food access showed no personality‐dependent differences in departure timing. Our results suggest that personality does not reflect intrinsic variation in spring migration timing, but rather interactions with environmental variation affecting the birds' ability to refuel body stores after food restrictions.