Fig. 3

a), b), and c) Onset of the pre-nuptial migration. Dates indicate when 5% more encounters than expected from the capture/observation of stationary individuals do occur; they have been calculated on the whole (a) or the rarefied (b) ringing dataset, or the eBird dataset (c). Isolines represent areas where the migration date occurs at the same time (e.g., in the central part of Sicily the onset of pre-nuptial migration occurs during the first ten days of January, while in the western and eastern parts of Sicily, it occurs during the second ten days of the same month). Months are divided into ten-day periods (‘decades’ sensu the Key Concepts Document of the EU Birds Directive; e.g. Jan 1, Jan 2, Jan 3). Isolines labels should be interpreted as the first day of the corresponding decade, e.g. isoline JAN1 should be read as “01 January”, JAN2 as “11 January”, JAN3 as “21 January” and so on. d), e) and f) Sensitivity analyses associated with panels a), b), and c), respectively. Isolines incorporate areas with the same sensitivity values (in days) of the estimated date of onset of the pre-nuptial migration