Do Blackbirds Signal Motivation to Fight with Their Song?
Article first published online: 12 OCT 2007
Volume 113, Issue 11, pages 1021–1028, November 2007
How to Cite
Ripmeester, E. A. P., De Vries, A. M. and Slabbekoorn, H. (2007), Do Blackbirds Signal Motivation to Fight with Their Song?. Ethology, 113: 1021–1028. doi: 10.1111/j.1439-0310.2007.01398.x
- Issue published online: 12 OCT 2007
- Article first published online: 12 OCT 2007
- Received: November 3, 2006 Initial acceptance: January 8, 2007 Final acceptance: April 21, 2007 (G. Beckers)
Conflicts about resources can be solved with physical fights, but animals will in general try to avoid them due to the costs and risks associated with fighting. Fight outcome depends on the fighting ability as well as the motivation to fight, which means that individuals should try to assess both during a pre-escalation phase. In the present study, we investigated whether blackbirds (Turdus merula) acoustically signal their motivation to fight with their advertisement song, which consists of a motif part with pure-toned low frequency elements followed by a twitter part with more complex and higher-pitched elements. We tested (1) whether the temporal and spectral characteristics of spontaneous songs broadcasted by a territorial male could predict its subsequent aggressive behaviour to a playback and (2) if the song of territorial males changed in case they responded aggressively to the playback. We found no effects in the temporal song structure, which contradicts results from a previous study involving playback experiments with blackbirds. We did however find an interesting pattern in the spectral characteristics of the twitter, since aggressively responding males significantly increased the twitter frequency after the playback. The post-playback songs of aggressive responders were nevertheless indistinguishable from spontaneous pre-playback songs of non-aggressive responders. Therefore, we conclude that changes in twitter frequency, rather than absolute twitter frequencies, are advertising information about motivation to fight.