Pigeon navigation: different routes lead to Frankfurt.
BACKGROUND
Tracks of pigeons homing to the Frankfurt loft revealed an odd phenomenon: whereas birds returning from the North approach their loft more or less directly in a broad front, pigeons returning from the South choose, from 25 km from home onward, either of two corridors, a direct one and one with a considerable detour to the West. This implies differences in the navigational process.


RESULTS
Pigeons released at sites at the beginning of the westerly corridor and in this corridor behave just like pigeons returning from farther south, deviating to the west before turning towards their loft. Birds released at sites within the straight corridors, in contrast, take more or less straight routes. The analysis of the short-term correlation dimension, a quantity reflecting the complexity of the system and with it, the number of factors involved in the navigational process, reveals that it is significantly larger in pigeons choosing the westerly corridor than in the birds flying straight - 3.03 vs. 2.85. The difference is small, however, suggesting a different interpretation of the same factors, with some birds apparently preferring particular factors over others.


CONCLUSIONS
The specific regional distribution of the factors which pigeons use to determine their home course seems to provide ambiguous information in the area 25 km south of the loft, resulting in the two corridors. Pigeons appear to navigate by deriving their routes directly from the locally available navigational factors which they interpret in an individual way. The fractal nature of the correlation dimensions indicates that the navigation process of pigeons is chaotic-deterministic; published tracks of migratory birds suggest that this may apply to avian navigation in general.
FB Biowissenschaften der Goethe-Universität Frankfurt, Siesmayerstraße 70, Frankfurt am Main, Germany; Queensland Brain Institute, University of Queensland, Building #79, St. Lucia, Queensland, Australia.
Ingo
I
Schiffner
FB Biowissenschaften der Goethe-Universität Frankfurt, Siesmayerstraße 70, Frankfurt am Main, Germany.
Roswitha
R
Wiltschko
D000818:Animals; D010856:Columbidae / Q000502:physiology*; D005260:Female; D005426:Flight, Animal / Q000502:physiology; D005858:Germany; D006702:Homing Behavior / Q000502:physiology; D008297:Male; D009949:Orientation / Q000502:physiology*; D065854:Spatial Navigation / Q000502:physiology*; D062211:Spatio-Temporal Analysis