DIFFERENTIAL EFFECTIVENESS OF PLAYBACKS FOR LITTLE OWLS (ATHENE NOCTUA) SURVEYS BEFORE AND AFTER SUNSET

摘要

Most nocturnal owls respond to broadcast of conspecific recordings, and this technique may be used to study their behavior (Galeotti and Pavan 1993, Galeotti et al. 1997), to map territories (Finck 1990, Lane et al. 2001), to identify individuals (Galeotti and Sacchi 2001, Delport et al. 2002), or to study population trends (Exo and Hennes 1978, Martinez and Zuberogoitia 2004). Several factors affecting the effectiveness of playback techniques or spontaneous vocalizations have been identified, including response distance (Proudfoot et al. 2002), season (Zuberogoitia and Campos 1998), weather (Lengane and Slater 2002), gender, and social status (Appleby and Red-path 1997). However, only a few studies have investigated systematically how these factorsinfluence playback methodology (McGarigal and Fraser 1985, Redpath 1994, Cen-tili 2001). When comparing the accuracy of sampling using spontaneous owl vocalizations or conspecific playbacks, several authors demonstrated that sampling error increases when using spontaneous calls (McGarigal and Fraser 1985, Haug and Didiuk 1993, Redpath 1994). However, for Eurasian Eagle-Owl (Bubo bubo), passive auditory surveys provide better results than surveys based on broadcast calls (Penteriani and Pichera 1991, Martinez and Zuberogoitia 2002).