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Résumé :
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As stated in early ornithology and ethology (Heinroth, Lorenz), the so-called Grunzpfiff or grunt-whistle is a common part of the display behaviour in male Mallards. It is shown by the birds in the preceding autumn and winter long before the beginning of the breeding period. It can be regarded as an exaggerated and enriched derivation of the normal body-shake displayed by all Anatidae species. The Grunzpfiff is part of the communal display behaviour in groups of male Mallards. In the behaviour pattern of grunt-whistle both movement and acoustical components are combined. During a forward bowing movement of the male, he pulls a string of water with the tip of his bill from the water surface. This water string then falls down in a series of drops on either side of the bird. This component is called water-flick display in English (Cramp and Simmons 1970). In addition to the movements, a whistle and then a low-pitch grunt are produced. These vocalizations are preceded and followed by two normal calls (‘rab’) of the male Mallard. The production of the whistle is not bound to a certain bowing phase of the male, as maintained by earlier observers, and it can be produced from the normal swimming position. Moreover, male Mallards and other male waterfowl] are not limited to producing high-pitched sounds but can utter deep-voiced vocalizations below 1kHz, which was recently shown also in male Mandarin Ducks (Aix galericulata,inprep.). In the course of their communal display, male Mallards synchronize their behaviour to a certain degree. However, only part of the whistles really overlap. A single male’s unusual behaviour was shown by video and sound analysis to include both whistles and ‘réb’-calls independently. They were repeated quickly and combined into varying patterns. Whistling calls are also produced by Mallard males in a number of other contexts.
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