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

Abstract

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.

Skill rather than beak kinematics affects seed handling performance in a granivorous songbird

“…Due to the nature of our data, we could not calculate marker‐to‐marker distance standard deviation as a measure of tracking precision (Knörlein et al, 2016). However, for a similar setup and calibration procedure, Mielke and Van Wassenbergh (2022) reported marker‐to‐marker distance standard deviations between 0.2 and 0.5 mm and, so we expect tracking precision to be similar here. As beak movements throughout the feeding act can be highly variable and irregular, five fragments of well‐tracked and relatively regular high‐frequency movements during seed positioning were selected per bird and per seed type for extraction of the kinematic metrics.…”

“…The importance of beak movement implies that the force–velocity trade‐off in lever systems will become relevant (Herrel et al, 2009). Seed‐eating performance will thus depend on many factors related to the mechanical capabilities and constraints of beak movement (Herrel et al, 2009; Mielke & Van Wassenbergh, 2022). Here, we use beak kinematics to refer to basic metrics of beak movement capacity such as maximal speed, acceleration and frequency.…”

“…However, with the technological advancements in high‐speed videography, automated tracking software (Knörlein et al, 2016) and machine learning (Mathis et al, 2018), such studies have recently become more feasible. An example thereof is the study by Mielke and Van Wassenbergh (2022), who recently analysed the three‐dimensional movements of canary beaks during feeding in a few individuals.…”

Upper beak depression instead of elevation dominates cranial kinesis in woodpeckers

“…the lower beak/jaw) depresses, and hence the two beak halves open or close in synchrony [1,6,7]. However, later studies showed an important level of independence in the control of upper and lower beak movement [3,[8][9][10][11].…”

“…skulls with a fixed upper beak) is not always clear, selective forces promoting cranial kinesis strongly depend on the ecological context [3]. Roles of cranial kinesis have been hypothesized in improving motion dynamics and control of food handling [1,[11][12][13][14], in sound production during singing [9] and in preventing injuries by shock absorption [1,15]. Mechanical trade-offs with other beak functions, however, cannot be excluded.…”