Seed preference is only weakly linked to seed-type-specific feeding performance in a songbird

The dehusking of seeds by granivorous songbirds is a complex process that requires fast, coordinated and sensory-feedback-controlled movements of beak and tongue. Hence, efficient seed handling requires a high degree of sensorimotoric skill and behavioural flexibility, since seeds vary considerably in size, shape and husk structure. To deal with this variability, individuals might specialise on specific seed types, which could result in greater seed handling efficiency of the preferred seed type, but lower efficiency for other seed types. To test this, we assessed seed preferences of canaries (Serinus canaria) through food choice experiments and related these to data of feeding performance, seed handling skills and beak kinematics during feeding on small, spindle-shaped canary seeds and larger, spheroid-shaped hemp seeds. We found great variety in seed preferences among individuals: some had no clear preference, while others almost exclusively fed on hemp seeds, or even prioritized novel seed types (millet seed). Surprisingly, we only observed few and weak effects of seed preference on feeding efficiency. This suggests that either the ability to handle seeds efficiently can be readily applied across various seed types, or alternatively, it may indicate that achieving high levels of seed-specific handling skills does not require extensive practice.

Methods

Food choice experiments were conducted where individual birds fed on a tray consisting of 9 different seed types for 10 minutes.
These experiments were recorded with a Sony RX1000M4 camera, and videos were manually analysed to count which seeds the individuals selected.
Data on seed choice was used to calculate Manly's Selectivity Index of 2 seed types (hemp and white millet) and Levin's niche breadth index.
These metrics were then related to data on feeding performance, seed handling skills and beak kinematics during feeding on canary seed and hemp seed. This data was taken from Andries et al. (2023).