Song in Swedish Great Tits: Intra- or Intersexual Communication?

This study examines the relative importance of song as a means of intra- as compared to intersexual communication in a Swedish population of great tits. Song duels and matched countersinging events did not occur more often than predicted by chance, in fact, neighbouring males tended to sing asynchrously in time. Males did not switch song type in association with change of song perch, contrary to the predictions of the Beau Geste hypothesis. Response to playback was generally low, and dependent of female presence. After pairing, males reduced their time spent singing by about 50%. When paired males temporarily lost contact with their mates, they greatly increased their singing rate. These observations show that song in Swedish great tits is primarily used as an intersexual signal, while in English populations, both functions are important. This difference is probably due to weaker competition for breeding space in the Swedish population in combination with a higher degree of movements during the non-breeding season.