Abstract. We investigated whether there are significant differences in neck muscle mass, maximum peck force, pressure and maximum pull force between Jungle Crows Corvus macrorhynchos and Carrion Crows C. corone. The maximum peck force and pressure were measured using pressure sensitive film. The maximum pull force was measured with spring balances. For male Jungle Crows, neck muscle mass, maximum peck force, pressure and maximum pull force were 8.27 g, 26.8 N, 80.4 MPa and 9.54 N; for females they were 6.82 g, 22.3 N, 69.7 MPa and 8.25 N. Those values for male Carrion Crows were 6.69 g, 22.3 N, 59.7 MPa and 4.07 N;, whereas for females they were 4.50 g, 15.1 N, 53.2 MPa and 2.71 N. Furthermore, neck muscle mass, maximum peck force and maximum pull force were positively correlated with body mass in both species. There were no significant differences in the ratio between the cervical levator mass and the cervical depressor mass, and the maximum peck force exerted by one unit of the cervical depressor mass between Jungle and Carrion Crows. However, the maximum pull force exerted by one unit of the cervical lavator and depressor mass of Jungle Crows was significantly larger than that of Carrion Crows.
Bird vocalizations are produced by contractions of syringeal muscles, which are controlled by the hypoglossal nucleus. In oscines, syringeal muscles are controlled by the hypoglossal nucleus ipsilaterally, whereas syringeal innervation is bilateral in non-oscines. We have determined the course of hypoglossal nerves in the jungle crow Corvus macrorhynchos . Our results indicate a cross-over of the hypoglossal nerve from the left side to the right side on the trachea 7 mm rostral to the Musculus sternotrachealis . We also investigated the innervation of the syringeal muscles of jungle crows from the hypoglossal nucleus using the horseradish peroxidase (HRP) method. After HRP was injected into the syringeal muscles on each side, HRP-labeled cells were found bilaterally in the hypoglossal nerve. These results suggest that the syringeal muscles of jungle crows are innervated bilaterally from the hypoglossal nucleus, although these birds are categorized as oscines.
Abstract. We investigated whether there are significant differences in jaw muscle mass, maximum bite force and pressure between Jungle Crows Corvus macrorhynchos and Carrion Crows C. corone. Maximum bite force and pressure were measured using pressure sensitive film. For male Jungle Crows, jaw muscle mass, maximum bite force and pressure were 2.36 g, 565.0 N and 127.2 MPa; for females they were 1.89 g, 398.5 N and 111.9 MPa. Those values for male Carrion Crows were 1.65 g, 424.3 N and 99.8 MPa; whereas for females they were 1.22 g, 298.0 N and 87.6 MPa. Furthermore, jaw muscle mass (P<0.05) and maximum bite force (P<0.05) were both positively correlated with body mass in both species. It is suggested that maximum bite force with respect to jaw muscle mass in Jungle Crows was significantly larger than that in Carrion Crows (P<0.05).
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