Van Eerden M.R., Zijlstra M. & Loonen M.J.J.E. (1991) Individual patterns of staging during autumn migration in relation to body condition in Greylag Geese Anser anser in The Netherlands. ARDEA 79 (2): 261-264

In autumn, the length of stay of individual Greylag Geese at the stopover site in Flevoland is related to the rate of increase in their body condition (Fig. 2). The condition was estimated by classifying the roundness of the abdominal profile (Fig. 1). At departure from our study area, the abdominal profile for all geese is approximately the same (Table 1), independent of the duration of the stay. Geese start their migration (to Spain) after reaching a certain threshold body condition.