大彎嘴 (Pomatorhinus erythrocnemis) 雄鳥歌曲歌型對應與歌曲重疊之意義

Abstract

Song type matching and song overlapping have been considered as aggressive signals in male songbirds. However, no studies have focused on the relationship between these two types of signals. To determine whether exposure to combine signaling increases aggression in songbirds, first, we evaluated the functions of song type matching and song overlapping in the Black-necklaced Scimitar Babblers (Pomatorhinus erythrocnemis). Second, we combined song type matching and song overlapping to examine is the combination a more aggressive signal. Lastly, we added overlapping in contest after type matching has already used for a while to examine that is song overlapping a second graded signal to escalate aggressive intention in the Black-necklaced Scimitar Babblers. The Black-necklaced Scimitar-Babblers, which exhibits strong reaction to intruders and possessed medium sized repertoire, was chosen as our subject. In the treatments interactive playback was used for recording their singing and behavioral responses. Field experiment was conducted during the breeding seasons of 2010 and 2011 at Wulai, New Taipei City, Taiwan. Interactive songs for playback were collected in Hsinchu, Yunlin and Chiayi. The results show that the male Black-necklaced Scimitar Babblers exhibited greater variation of song interval (P=0.011) and spent more time in a 10-meter circle from the speaker (P=0.039) when song-type matching treatments were conducted. Males did not exhibit responses that were different from control treatments compare to song overlapping treatments. However, when song overlapping and song type matching happened simultaneously, males exhibited shorter songs (P=0.030); when song overlapping was added in after song type matching had continued for a while, males responded stronger that they exhibited more number of songs (P=0.0005) and spent more time in a 10-meter circle from the speaker during playback (P=0.033) and post-playback period (P=0.033). We conclude that in song contests of the male Black-necklaced Scimitar Babblers, song-type matching may serve as an aggressive signal. Overlapping may serve as an aggressive signal if happens with song type matching simultaneously or with song type matching continues for a while. We conclude that song overlapping is a second graded signal to escalate aggressive intention in the Black-necklaced Scimitar Babblers if necessary.