All 16 acoustic variables showed a higher coefficient of variation among individuals. In addition, we conducted a series of 15 a stepwise discriminant function analysis (DFA) models. We calculated the Potential for Individual Coding (PIC) comparing the coefficient of variation both within and among individuals. We analyzed 217 hissing sounds from 22 individual geese. Therefore, we aimed to test whether non-vocal air expirations can encode an individual’s identity similar to those sounds generated by the syrinx or the larynx. Compared to vocally produced alarm calls, almost nothing is known about how non-vocal hissing sounds potentially encode information about a caller’s identity. This bird represents a ground nesting non-passerine bird which frequently produces hissing out of the nest in comparison to passerines producing hissing during nesting in holes e.g., parids. Presently, only the hissing of small, nesting passerines as a defense against their respective predators have been studied. Even though hissing sounds have been studied in mammals and reptiles, only a few studies have analyzed hissing sounds in birds. These noises often emulate whispering, snorting or hissing. Besides mechanical sounds produced by feathers, bills and/or wings, sounds can be also produced by constriction, anywhere along the pathway from the lungs to the lips or nostrils (in mammals), or to the bill (in birds), resulting in turbulent, aerodynamic sounds. Furthermore, some birds are known to produce several types of non-syrinx sounds. Some sounds made by terrestrial vertebrates are produced not only by the larynx but also by the syrinx. Non-vocal, or unvoiced, signals surprisingly have received very little attention until recently especially when compared to other acoustic signals.
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