Interactions between males are important part of everyday life in birds. Correct recognition and assessment of the rival is a key step in the interaction. Wrong assessment of the rival and consequently wrong decision about a way of proceeding in the interaction (escalation, retreat) can lead to significant energy loss, loss of territory or even injuries or dead. Recognition based on acoustic signals has a great advantage – males do not need even to show up to their rivals and put themselves in a potential risk. We focus on acoustic signals in our studies of rival recognition and assessment.

Neighbouring males are probably the most often encountered rivals. Ability to discriminate neighbours from strangers is beneficial to males as they need to focus mainly on deterring stranger males. Neighbours are generally considered to be “dear enemies” who respect established rules. The fact that male songbirds can recognize their neighbours by song is widely accepted. Which parameters code individuality is not clear, however, and many song parameters such as spectral parameters, temporal parameters, specific elements, etc. were proposed but scarcely tested as individuality carriers.

Males can also benefit from correct assessment of competition qualities like size, endurance, etc. or motivation of their rivals. For instance, frequency of the acoustic signals correlates with body size and can be therefore used to assess rival size in many animal species. As bigger males usually win in physical confrontation it is better to stay away from the individuals with low-pitched voices. We look at how competition qualities and motivation might be coded in songs of songbird males and whether they can extract this information during contests.