Three-dimensional movement of the beak during seed processing in domestic canaries.

Many songbird species rely on seeds as a primary food source and the process of picking up, positioning, cracking, dehusking and swallowing seeds is one of the most sophisticated tasks of the beak. Still, we lack understanding about how granivorous songbirds move their beak during the different phases of seed processing. In this study, we used multi-view high-speed imaging to analyze the 3D movement of the beak in feeding domestic canaries. Our analysis focused on the correlation of the upper and lower beak, the frequency of mandibulation and the direction of mandible movement in 3D space. We show that the correlation of maxilla and mandible movement differs among the phases of seed processing. Furthermore, we found that the beak moves at extremely high frequencies, up to 25 Hz, which resembles previously reported maximal syllable rates in singing canaries. Finally, we report that canaries use specific 3D mandible movements during the different phases of seed processing. Kinematic parameters do not differ between male and female canaries. Our findings provide an important biomechanical basis for better understanding the beak as a functional tool.