The influence of repeated releases on the homing behaviour of sand martins(Riparia riparia)

Data on the effect of repeated releases on the homing behaviour of sand mar tins released four times from the same site (beyond 50 km from the nesting colony) are presented. The results, obtained by two series of releases, sho w a progressive improvement of both the initial orientation and the homing performances. When the birds released four times from the same site were di splaced in a new site, Located roughly at the same distance, but in the opp osite direction to the former, they do not change directional preferences w ith respect to the Last experimental release, the homing speeds were also n ot different to those recorded for birds without any release experience. Wh ile the learning of orienting cues can not be excluded, the data point out that the habituation to the handling stress and a form of directional train ing seem to play a major role in determining the observed behaviour. The fa miliarity with a site does not seem to improve the homing behaviour of sand martins when released from a different one.