Songbirds may have developed sharper senses to de-husk seeds

Songbirds, members of the Passeriformes order, are renowned for their complex vocal abilities. However, certain species possess an additional skill: the ability to easily remove the tough outer layer, or husk, from seeds before consuming the nutritious interior. Researchers from the University of Alberta, the University of Lethbridge, and the Catholic University of Chile investigated brain differences among 92 songbird species to understand the evolutionary basis of this seed-dehusking capability.

Their study, published in Proceedings of the Royal Society B, indicates that the enhanced tactile sense of these birds, rather than more robust or advanced movements, underpins their seed-dehusking skills. Cristián Gutiérrez-Ibáñez, a co-author of the paper, explained that the team focused on the evolution of sensory systems in birds and dehusking as a prime example of skilled manipulation driven by brain changes.

The researchers examined brain slices from various songbird species, measuring the volume of brain areas responsible for processing touch information from the beak and tongue (sensory nuclei) and controlling movement of these body parts (motor nuclei). They discovered that in species capable of dehusking seeds, the sensory nuclei associated with the tongue were significantly larger than those in non-dehusking species.

This enlargement suggests that touch-related information plays a crucial role in the birds' ability to manipulate seeds, akin to the enlarged fingertips of primates for object manipulation. Interestingly, the motor nuclei controlling beak and tongue movements did not show significant enlargement in seed-dehusking birds, implying that enhanced tactile processing, not motor specialization, facilitates this behavior.

Future research could explore the distribution of touch receptors in the tongues of these birds, study other species capable of seed-dehusking, and examine similar abilities in non-songbird species like parrots.