Functions and costs ensuring signal reliability of so-called soft song in agonistic interactions in birds
Project duration: 2014-2017
Head of the project: Tomasz Osiejuk
Co-workers: Aleksandra Jakubowska, Katarzyna Kwiatkowska
The aim of the project is (1) to provide qualitative and quantitative descriptions of the so-called soft song, produced in agonistic contexts by birds, and (2) experimental verification of the functions of the bird’s soft song, produced in agonistic contexts. The model species will be the ortolan bunting, which was found producing a low-amplitude song while defending its territory in our earlier research. Six different hypotheses have been given for this phenomenon. Soft song used for defence seems to be common and widespread in animals but is rarely studied because of its specific character and methodological constraints. Not all hypotheses explaining soft song are mutually exclusive. Some of them simply concern different aspects of this phenomenon, e.g. mechanisms, evolution or costs. One hypothesis even questions the assumption that low-amplitude has evolved as an inherent part of the signal, suggesting instead that low-amplitude is only a by-product of the readiness to fight with a rival. For now, we can conclude that soft songs (and other similar low-amplitude acoustic signals) are probably common and used in agonistic contexts by animals. These songs seem to be the best predictor of increased aggressiveness and further physical fighting. For this reason, the soft songs are of crucial importance and affect the fitness of an individual. There are a few, somewhat different ideas, for explaining how such signals work and for explaining the costs involved in maintaining their reliability. Thorough experimental research on different model species is definitely needed to clarify all doubts and put the missing link of territorial behaviour on its right place.