Figure 1.

(a) Desertas petrels' tracks. The blue dots represent the locations classified as ‘searching’. The yellow rhombus shows the breeding colony on Bugio Island. (b) The random (top) and rotated (bottom) simulated trips based on an example track. The real trip is depicted in blue, the simulated ones in light grey. Of the rotated tracks, the ones that would grant the bird a higher mean speed are depicted in red. For clarity, only a subset of the 100 rotated tracks is displayed. (Online version in colour.)