The sound-producing organ of birds is called the vocal head . The scientific name Syrinx is derived from the panpipe , which is also called Syrinx after a Greek nymph . The vocal head is also known as the lower larynx . The actual, "upper" larynx in birds serves exclusively to separate the air and food pathways and not for voice formation, it also has no vocal cords (vocal folds, vocal folds).
In most birds, the vocal head is due to the division of the windpipe ( trachea ) into the two main bronchi (so-called tracheobronchal vocal head). In some species it is located directly in the trachea (tracheal vocal head), in some more in the main bronchi (bronchial vocal head).
The tracheobronchal syrinx begins with a compact cavity, the tympanum (2). It is created by the fusion of the posterior rings of the trachea. In male ducks the tympanum has a left-sided enlargement ( bulla syringealis ). Inside there is a bony bar, the pessulus (4) , where the main bronchi are split . The syrinx rings , which are divided into two groups, continue from the tympanum to the bronchi (3, 7). A membrane , the lateral tympaniform membrane (5), is clamped between the two groups . A medial tympaniform membrane (6) is also stretched out on the inside . It continues down into the connective tissue that closes the C-shaped bronchial cartilage (9).
The tension of the four syrinx membranes can be changed by muscles. High-frequency expiration triggers vibrations in these membranes, which are modulated by the muscles and, in their entirety, produce the species-specific song of the birds. These bird calls are often so characteristic that a species identification is possible from the singing alone, without the bird having to be seen.
A number of birds are able to operate the syrinx membranes on both sides independently of each other and thus produce two-part chants. Cowbird (genus Molothrus ) alternately use the left and right side, so that they can generate very fast tone sequences (up to 30 tones per second).
Other mechanisms of sound generation
In addition to the actual vocal organ, birds use other mechanisms to generate sounds, such as:
- Stamping with the foot (e.g. coot )
- Rattling of the jaws , i.e. the upper and lower beak (e.g. storks , frigate birds , owls )
- Wing flapping (e.g. wood pigeon ), in some species specialized feathers are designed to produce sounds
- Knocking noises ( woodpeckers )
- Franz-Viktor Salomon, Maria-Elisabeth Krautwald-Junghanns: Anatomy of the birds. In: In: Franz-Viktor Salomon, Hans Geyer, Uwe Gille (ed.): Anatomy for veterinary medicine. 2nd, revised and expanded edition. Enke, Stuttgart 2008, ISBN 978-3-8304-1075-1 , pp. 754-814.