Structure of the syringeal muscles in jungle crow (Corvus macrorhynchos).

Birds' vocalizations are produced by the syrinx, which is located between the trachea and the two primary bronchi. Oscine birds have multiple pairs of syringeal muscles in the syrinx. To determine the detailed structure of the syringeal muscle in jungle crows, an oscine bird, a histological study and gross examination of the syrinx were performed. In the histological study, sections of the syrinxes from four jungle crows were stained with Azan and observed. Each syringeal muscle was classified by the limit of the fascia from neighbor fascicules. From the gross examination a 3-D image of the structure of the syringeal muscles was generated. The combined histological and anatomical results show that there are seven pairs of syringeal muscles in jungle crows. Muscle fusions were observed in some of the syringeal muscles. It is likely that each syringeal muscle has a specific role. Jungle crows may be able to generate various calls because they have several pairs of syringeal muscles.