Articulatory patterns during contact call production. Contact calls (A) are accompanied by movements of different articulators (B). Most prominently, beak opening (BO) increases while tongue height (TH) decreases and the trachea contracts (TS) over the course of a contact call, while the larynx, similarly to the tongue, moves downwards (LM), thereby increasing the distance to the dorsal beak–skull transition. Interestingly, the onset of movement of these articulators starts before the onset of the call so as to prepare the vocal tract for the subsequent sound production.

Articulatory patterns during greeting call production. Greeting calls (A) are accompanied by changes in the same articulators (B) as for contact calls. However, greeting calls are often of a longer duration and over the course of longer greeting calls beak opening (BO) and laryngeal movement (LM) proceed more gradually while the tongue depresses (TH) at call onset and remains low during call production.

Articulatory patterns during chatter sounds. This figure represents articulatory movements (B) during the production of two alternating chatter sounds (A) of bird 1. Note that both beak (BO) and tongue (TH) reach their maximum displacement just after the onset of the sound while most of the sound is produced when these articulators are moving back to their original position. Laryngeal movement (LM), however, exhibits this pattern only for the second and fourth note while it seems delayed relative to the other articulators in the first and third note. It is also noticeable that the magnitude of articulator displacement varies between the two note types and is larger for the first and third note than for the second and fourth note.

X-ray images. This figure shows two X-ray frames of the same monk parakeet (A) prior to vocalizing and (B) during contact call production. Beak, tongue and trachea are outlined in black. The dark dot on top of the head is the metal sphere used as a size reference.