The initial orientation of breeding sand martins (Riparia riparia) released at short distances (4.2-12.3 km) from their home colony was significantly affect-ed by treatments that apparently did not interfere with their homing process (transport to the release site in total darkness and/or inside transparent bags). Compared to the behaviour of birds transported in daylight inside semitranspar-ent bags, both treatments worsened the degree of homeward orientation and increased the sand martins' tendency to fly in the preferred compass direction. These results supported previous findings collected on homing pigeons and indi-cated that emotional components could also play a role in determining the ini-tial orientation in free-living birds. Considering the widespread occurrence of home-independent orientation in the few wild species whose homing behaviour has been rather intensively studied, these data suggested that stress-induced phe-nomena are a serious obstacle to a proper comparative analysis of the homing mechanism of birds.