Homing paths of unmanipulated control birds (C3, C4, C5, C6, C7, C8, upper panel) and birds carrying mobile magnets (M2, M3, M4, M5, M8, lower panel) plotted over a Google Earth map. See supplementary material Table S1 for details. The yellow circle indicates the home colony. For birds that homed but were not tracked as far as the home island, broken lines link the last location obtained and the colony. Thick lines represent the oceanic journey; thin lines represent the track recorded after the bird got closer than 50 km to any one of the islands of the Azores Archipelago. For each bird, colour-coded dates of release and of the last fix recorded are reported.
Tracks of anosmic birds (A2, A3, A5, A6, A7, A8) (see supplementary material Table S1 for details). The green circle indicates the home colony. The insets show the area near the Azores islands at greater magnification (see Results for other explanations). Faial is the home island. The A3 track is reported only until the bird approached the colony site more than 3 months later, when the reproductive period was over and its olfactory mucosa should have been reconstituted. The complete track of this bird is reported in supplementary material Fig. S1. Other explanations as in Fig. 1.
Mean ± s.e.m. distance from the colony, expressed as a percentage of the distance at the release site, of the three groups of shearwaters (C, un-manipulated controls; M, birds bearing mobile magnets; A, anosmic birds) from the time of release (indicated by 0) up to day 5 after release.
Orientation of the tracks in open ocean (C, control birds; M, birds bearing magnets; A, anosmic birds; A-5 days, anosmic birds in the first days after release). Each mean vector indicates the mean orientation of a bird's track. The mean vector distributions were tested for randomness with the Hotelling test (confidence ellipses are shown). Triangles at the periphery of the circles represent the mean directions of the tracks. Second-order mean vector length (r) and direction (α) are given.
Sections of tracks of control (upper panel) and magnetic (lower panel) shearwaters after the birds had approached any island of the archipelago. The tracks are plotted over a magnified map of the Azores Archipelago area. Other explanations as in Fig. 1.