Homing flights of pigeons over familiar terrain

The routes of nine adult pigeons repeatedly released from a familiar site 9.1 km west of their Frankfurt home loft were recorded with the help of GPS-based flight recorders. Analysis of the tracks shows considerable variability not only between individual birds, but also between the tracks of each individual concerning duration of flight, flying speed and the routes chosen. The efficiencies (direct route divided by length of the route taken) are fairly high, ranging from 0.77 to 0.91. They did not increase significantly, nor did the tracks become more similar, as the pigeons became more familiar with the area between the release site and the loft. Homing flights begin with a starting phase of lower efficiency. Five hundred metres from the release point, all birds were significantly oriented; at 2500 m, they showed a small southerly deviation from the home direction. The overland flights were mostly very straight, with efficiencies above 0.9, and so was the approach to the loft. The flying corridor crossed the western suburbs of metropolitan Frankfurt, rich with conspicuous landmarks and highways, but an obvious influence of these features was not observed. In contrast to what was reported from other areas, our pigeons did not show a pronounced tendency to follow highways. Loops and detours in the course of the return flights are in part attributed to social interactions with other pigeons.