The pigeon syrinx is markedly different to that organ in most other birds, and although basically a simple structure, shows a number of unique modifications, the significance of which cannot readily be fully assessed. The tracheal rings are dorsally cartilaginous, but are thickened and ossified over their ventral surfaces; the sternotrachealis muscles are asymmetrically inserted on to the trachea. There is an extensive unsupported area in the external walls of the syrinx, resembling an external tympaniform membrane, but which does not appear to be a sound source. The tracheolateralis muscles insert directly on to this area, not on to the adjacent rings. There is no rigid pessulus.
The sound-producing mechanism of the Columbidae is different to that found in other non-passerine birds. The anatomy of the syrinx is described in detail, and the mechanism of sound-production is discussed.