Functionally similar acoustic signals in the corncrake (Crex crex) transmit information about different states of the sender during aggressive interactions

►We combine playback experiments with hormonal manipulations. ►We study the information content of acoustic signals during aggressive interactions. ►Testosterone blockage limits aggressiveness of males and frequency of soft calling. ►Increased levels of testosterone neither affect calling nor male's aggressiveness. ►Soft calls and broadcast calls transmit different information.