30.04.2024: The way birds sing is important in mate choice. This is well-known from behavioural research. But what characteristics of birdsong are important for competition between male birds? An international study led by the University of Veterinary Medicine Vienna used a playback experiment to investigate this question using reed warblers (Acrocephalus scirpaceus) - a native songbird that overwinters in sub-Saharan Africa. According to the study, monotonous repetitions of bird song syllables convey dominance. So, do stereotypical singers have an advantage?

In behavioural research, the virtuosity (complexity) with which a male bird performs his song has long been identified as an important criterion in female mate choice. In contrast, the role of song in interactions between rivals is less clear - and very little is known about which song characteristics are particularly important in territory defence and confrontations between males.

One way of getting your point of view and opinions across to the ‘man’ (addressee) clearly and emphatically is to repeat the ‘message’ to be conveyed. We humans also use repetition to emphasise statements and make them more credible. In reed warblers, males increase their song complexity to impress females, while they reduce it in territorial disputes. One way to reduce song complexity is by repeating individual syllables. In their recently published study, the team of scientists therefore investigated the importance of repeating syllables during territorial disputes with rivals.

Playback experiment with different frequencies of syllable repetition

The researchers hypothesised that the repetition of syllables signals a male's general fighting ability, aggressive status, or willingness to attack. Study lead author Herbert Hoi from the Konrad-Lorenz Institute of Ethology (KLIVV) at Vetmeduni explains: ‘In a playback experiment, we investigated the behavioural response of unmated, territorial reed warbler males to two intruders singing at the same time, whereby the song of the two intruders simulated by playbacks differed in the extent of syllable repetition.’

A clear behavioural response: those who repeat themselves demonstrate dominance

The reaction of the territory holder was determined using several behavioural parameters. The results showed that the complexity of the song does not play a role in whether the males dare to approach the playback or how close they come. However, it turned out that territory holders approached more quickly and stayed significantly longer in the vicinity of the complex playback song, i.e. the one with few repetitions.

‘This weaker response to the song with many repeated syllables suggests that territorial males are more intimidated by the aggressive nature of this type of song,’ says Herbert Hoi. However, as the other differences in response were rather weak in relation to the extremely divergent song characteristics in the playback experiment, Hoi believes that it would be interesting for future studies to investigate the social status and motivation of those males that seek the proximity of a conspecific that embodies one or the other song type.

 

Scientific article