Physiological measures for migratory and reproductive preparedness
Resident cloacal protuberance volumes and testosterone were both higher than migrants (CPV, p = 0.0006; T, p = 0.002; Student t -test; Fig. 3 a, b; Table S1), confirming that they were at a more advanced stage of reproduction at the time of sampling. There was no difference in body mass between migrants and residents (Fig. 3 c; Table S1), but the fat score was significantly higher in migrants than residents (p = 0.02; Student t -test; Fig. 3 d; Table S1),