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 three-dimensional movement of the beak
in feeding domestic canaries. Our analysis focuses on correlation of upper
and lower beak, frequency of mandibulation, and 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.