RELEASE EXPERIMENTS WITH WILD ROCK DOVES (COLUMBA L. LIVIA GM.)

The homing behaviour of free-living birds has rarely been systematically investigated, and so it is difficult to give a satisfactory comparative picture. Data are here presented on the initial orientation of rock doves displaced inside and outside the area that they daily cross during their foraging flights. Inside the familiar area, the results show marked variability in the directional choices of the released birds, probably related to temporal variability in the location of food patches during the year. Indeed, in autumn, when the doves feed almost exclusively near the colony site, they tend to fly home, but in summer, when food patches are dispersed over a wide area around the colony, this behaviour is not evident. Outside the familiar area, no clear evidence of a homeward directedness is obtained. Two releases inside the familiar area with clock-shifted birds produced ambiguous results and it is difficult to attribute the behaviour of the animals to a change in their motivation to reach home in different times of the day, or to the use of a timecompensated sun compass. On the whole, the presented results point to the difficulties of comparing rock dove behaviour to that of the homing pigeon, and show the importance of considering the influence of ecological and motivational variables in evaluating the orienting performances of wild birds.