Signal complexity communicates aggressive intent during contests, but the process is disrupted by noise

Abstract

Contestants use displays to signal their aggressive intent and settle disputes before they escalate. For birds, this is often in the form of song, which can vary in structural complexity. The role of song complexity in signalling aggressive intent has not been fully established, and its efficacy could be influenced by background noise levels. Using playback experiments, we found that in European robins, Erithacus rubecula, song complexity signalled sender aggression and affected receiver response. However, increased noise impacted the ability of contestants to adjust response based on opponent song complexity. These findings provide new evidence regarding the use of acoustic signal complexity for assessing opponent aggression and that noise can influence contest behaviour by interrupting this process, which could impose fitness consequences.

Electrocommunication signals indicate motivation to compete during dyadic interactions of an electric fish

“…In A. leptorhynchus subordinates could emit rises to signal their motivation to continue assessment, with the aim to reduce relative dominance (e.g. Kareklas et al, 2019). Dominants, on the other hand, could counteract with agonistic attacks.…”

Tape lures swell bycatch on a Mediterranean island harbouring illegal bird trapping

“…Birdsong functions in mate choice and territory defence [35,36], so theoretically should only attract conspecific birds, and their close competitors (e.g. [37]).…”

Electrocommunication signals indicate motivation to compete during dyadic interactions of an electric fish

“…In A. leptorhynchus subordinates could emit rises to signal their motivation to continue assessment, with the aim to reduce relative dominance (e.g. Kareklas et al, 2019). Dominant fish, on the other hand, counteract with agonistic attacks (e.g.…”

“…They can directly indicate and reflect an individual's RHP (Davies and Halliday, 1978;Clutton-Brock et al, 1979), but also convey information about additional factors influencing a contest and its outcome, like motivation and behavioral intent (e.g. aggression: Kareklas et al, 2019;Westby andBox, 1970, or submission: Hupé andLewis, 2008;Batista et al, 2012) or social status (Fernald, 2014). Such low cost signals have been shown to reduce the intensity and duration of contests or even convey sufficient information to resolve conflicts without the necessity of physical competitions (Parker, 1974;Clutton-Brock et al, 1979;Janson, 1990).…”