Fig. 2

Arrival fuel loads (relative values) of migrating blackbirds caught on Helgoland during a) autumn (n = 919) and b) spring migration (n = 393). Age differentiation is only possible in autumn (first-years n = 461; adults n = 458). The curved lines represent the kernel density estimates, i.e. the smoothed version of the histograms. The dashed lines describe the fuel loads needed to reach the different coastal destinations (Fig. 1) in still air (zero flow-assistance): a from left to right Wangerooge, Juist, Terschelling and Caister-on-Sea; b St. Peter-Ording, Amrum, Blåvand and Mandal