Fig. 2

Different extents of pre-migratory flights might serve different functions. For the case of our model, a woodland thrush, suitable habitat is shown in orange, and unsuitable habitat is shown in blue. The bird takes off from its starting point (solid white line) and the extent of its movement depends on the function of the flight. A Small-scale flights serve to practice flying at night, assessing meteorological conditions, or are a function of avoiding a perceived threat and likely terminate at or near the starting location. B Intermediate- and large-scale movements serve to practice and assess orientation skills and form landscape or magnetic maps; the scale to which they occur may depend on the surrounding landscape or the existing status of an individual’s internal maps. The scale of flights that serve to practice selecting suitable habitat in darkness may depend on the extent to which surrounding habitat is contiguous. For illustrative purposes, we show these larger-scale flights terminating far from the starting point, though an individual may instead circle back. Although the intermediate flight, B, shows the bird landing in unsuitable habitat, this does not suggest that all flights on this scale terminate in unfavourable landscapes, merely that landing in unsuitable habitat is a possible outcome in the context of pre-migratory flights