Fig. 5

Difference in a) departure date, b) return date, and c) migration distance for migratory yellow-legged gulls from oiled (n = 6) and non-oiled (n = 5) nests on Frioul, Marseille, France, 2021 (Y1)-2022 (Y2). Shaded bands indicate 95% confidence intervals of trendlines. The oiled group were subject to egg-oiling treatment in Y1 but not Y2, while the non-oiled group did not receive egg-oiling treatment in either year. The interaction of year with oiling status was a significant predictor of departure date, but not of return date or migration distance (see Table S2)