Fig. 2

Migration of Pink-footed geese in their first GPS-tracked spring and following springs. The individual change in spring migration timing, from the first to the following springs, differed between geese tagged in summer (Svalbard, migrating via Trøndelag; left half of each panel, with shaded background) and geese tagged in spring (Oulu and Trøndelag; right half of each panel). Geese tagged in summer showed no delay in their migration timing when we compare their first versus next springs, but geese tagged in spring did. This pattern was visible in the departure date (A), the arrival date (B), but not the migration duration (C). The pattern indicates that the initial delay (red diamond) is not simply an effect of ageing (i.e., delayed migration at younger age), but more likely a tagging effect. Sample sizes are given on the bottom as number of individuals, with the number of tracks in brackets (as some individuals migrated in multiple following springs, more detail in Additional file 1: Table S2). Boxplots and means ± SE are given. The p-value of the interaction tagging season × spring group is given on the top and was based on LMMs including a fixed effect of stopover and random effects of individual and year