Preliminary Qualitative Evaluation of the Anatomical Structures for Vocalization in the Chicken (Gallus gallus domestica)

The anatomical structure of phonation in the domestic chicken Gallus gallus (red jungle fowl, forma domestica) of both sexes was studied to determine sex variations in structures. Ten (10) birds, involving 5 males and 5 females were obtained from a local market for student demonstrations and used for this study. Tracheal rings were observed to be made of circular cartilages numbering thirty and above with the distal most (1/5) tracheal rings narrowed, calcified and fused as the tympanum making part of the Syrinx. The rings become calcified and somewhat collapsed through the bronchial bifurcations. When squeezed, the trachea collapsed completely between fingers but could at releasing the fingers be raised up due to elastic components separating the rings from one another. Other structures involved in vocalization includes straps of muscles. Male structures involved in respiration and vocalization were well formed compared to those of the female. Both tracheobronchialis lateralis and ventralis muscles were thicker than those of the female. Male tracheobronchialis ventralis and dorsalis muscles were well formed and spindle shaped. However, the female tracheobronchialis muscles were seen to be wider compared to the male. The vocal organs (voice box) were seen to be arbitrarily triangular in structure at the bifurcation of the trachea in both sexes. The male Syringeal walls were thinner and were seen to have marked inter Pessula space. The Pessulus mark an abrupt change from the circular trachea to strongly elliptical entrances to the bronchi. It was concluded that the differences in the thinness of syringeal walls coupled with differences between the males and females in other tracheal muscles might be responsible for the stronger vocalization in the male.