Corncrake males learn new signal meanings during aggressive interactions

• I tested comprehension and usage of a new syntactic code in a nonpasserine bird.
• Conditioning combined playback and movement stimulation.
• Males comprehended and used a new code after only a few minutes of exposure.
• Corncrakes' innate calls allow them to learn the temporal patterns of calls.

For many animals, the repertoires of songs or calls are relatively small and static during a lifetime. One reason for this is that there are different physiological limitations in the respiratory, phonatory and filter systems in different phylogenetic groups. Nevertheless, learning does not have to be associated exclusively with the acquisition of new vocalizations; individuals may recombine a limited number of elements already present in an individual's repertoire into new sequences. I tested the possibility of learning timing of calls in the corncrake, Crex crex, a nonpasserine bird with an extremely low repertoire of calls, using temporal patterns of calls during territorial interactions. I tested whether male are able to comprehend and use a new pattern by connecting known syntax with a new meaning through experience. Experiments with playback demonstrated that males were able to comprehend a new association between the temporal pattern and approaching behaviour of the intruder only after a few minutes of exposure to new circumstances. Additionally, apart from comprehending, males acquired a new signalling strategy; they began signalling their aggressive motivation using the new association. Because comprehension and usage of associations between the syntax of vocalizations and the approaching behaviour of males were modifiable as a result of experience, these results indicate that corncrakes' innate call structures and lack of complex and variable songs allow them to learn the temporal distribution of their calls. This suggests a much broader application and a vital role of contextual learning for the evolution of simple acoustic signalling systems.