Ecology and Brain Size Drive Feeding Innovations in Birds.

Feeding innovations, reflecting behavioral plasticity, are crucial for animals adapting to rapidly changing environments. Although larger brains are theorized to enhance adaptability by increasing behavioral flexibility, the combined influences of brain size and ecological factors on feeding innovations remains poorly understood. Birds, with their well-documented feeding innovations, offer an ideal study system to explore these relationships. Here, we analyzed feeding innovations across 955 bird species, examining relationships with brain size and ecological variables. Our results reveal that residual brain size positively correlates with feeding innovation rate. A high feeding innovation rate is commonly observed in resident species that employ omnivorous feeding strategies. Moreover, the patterns of association with residual brain size and ecological variables differed between the two innovation subtypes, namely technical and food type innovation rates. Phylogenetic path analysis further indicates that the effects of residual brain size and temperature seasonality on feeding innovation are mediated via migration type and/or feeding strategy. Together, our findings suggest that cognitive abilities, regulated by residual brain size, interact with ecological factors to shape feeding innovations, ultimately facilitating birds' adaptation to environmental changes.