Sounds of passerine and non-passerine birds may provide data on body condition of a bird. Information about organism quality may be encoded by different ways. For example, a greater bird should have greater syrinx that lead to lower main frequency of sounds. Second, a longer trachea corresponds to smaller formant dispersion. More than 60 bird species have a tracheal elongation i.e. loops of trachea inside of sternum. Fitch (2000) suggested hypothesis that tracheal elongation is a way to imitate sounds of greater animal due to formant dispersion decreasing. We analyzed correlation of body mass and sound parameters in the calls of white-naped crane Grus vipio. We recorded calls of 6 captive breeding pairs i.e. 12 adult cranes. We described vocal repertoire of white-naped crane as five types of single calls and duet call - stable sequence of single calls. There are three tonal calls (guard call, bark and buzzing) and two non-tonal, rhythmical calls (purring and quacking). Non-tonal rhythmical calls are more suitable for highlighting of formants that tonal calls. We found that none of parameters of tonal calls correlated with body mass. At once, peak frequency of purring significantly correlated with body mass. Frequency parameters of duet calls significantly correlated with body mass. We suggested that sound duration should be connected with body condition. A greater animal have greater lung volume and can call longer. Nevertheless, none of call types had duration correlated with body mass. Thus, (1) peak frequency of purring correlated with body mass that support hypothesis of vocal size exaggeration and (2) duet call of white-naped crane provide information about body mass.
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