This is the pipping stage of egg development, and, in fact, it is this vocal communication among un- hatched siblings that enables their synchronized hatching (see sidebar). Two days before hatching, the young are fully capable of hearing this call and begin to make their own vocalizations, which can be heard by the other unhatched ducklings. As a hen sits on her nest, incubating her eggs, she exposes the embryos to her maternal call. Therefore, voice and hearing development in waterfowl begins early. For example, the slow raehb-raehb-raehb call is used by the drake mallard to draw attention to himself for the purpose of attracting a mate, but this same call is also used to alert other mallards of the presence of a predator.Ĭommunication between members of a species is crucial to survival. The call repertoire of waterfowl is somewhat limited often the same call is used in a variety of circumstances. Similarly, a female mallard does not produce the grunt-whistle vocalization used by the male mallard during courtship displays. Male wood ducks are physically incapable of producing this call. Many of us are familiar with the high-intensity squealing call the female wood duck makes when it is disturbed. Males and females of most species of waterfowl have distinctly different calls because of physical differences in the trachea and the syrinx. The shape of the syrinx and the muscles that control membrane tension dictate the different calls within and between species. Calls are produced as air passes over the membranes of the syrinx, causing them to vibrate. The syrinx is located in the throat, at the bottom of the trachea near the junction of the bronchial tubes. The vocal organs of waterfowl consist of simple membranes located in a structure called the syrinx. Waterfowl use these vocalizations in a variety of situations as a primary means of conveying information. Vocalizations of waterfowl are considered calls rather than songs because they are short and instinctive in nature. But how do waterfowl use these vocalizations, and what do they mean? Why does each species have its own intrinsic calls? Why do males and females of the same species make different sounds? The unmistakable honk of a Canada goose as it flies overhead and the raspy decrescendo call of a hen mallard are two familiar waterfowl vocalizations that humans use to identify these birds.
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