Abstract
We analyse the tracks of clock-shifted pigeons from six releases to determine how pigeons cope with the conflict between their sun compass and the other navigational cues. Time-lag embedding is used to calculate the short-term correlation dimension, a parameter that reflects the complexity of the navigational system and with it, the number of factors involved. In the beginning, while pigeons are still at the release site, the short-term correlation dimension is low; it increases as the birds leave the site, indicating the birds are now actively navigating. Clock-shifted pigeons show more scatter than the control birds, and their short-term correlation dimension becomes significantly smaller than that of the controls, remaining lower until the experimental birds reach their loft. This difference is small, but consistent and suggests a different rating and ranking of the navigational cues. Clock-shifted pigeons do not seem to simply ignore the information from their manipulated sun compass altogether, but appear to merely downgrade it in favour of other cues, like their magnetic compass. This is supported by observation that the final part of the tracks still shows a small deviation into the expected direction, indicating an effect of clock-shifting until the end of the homing flight.