Numerical cognition in birds

Avian species are one of the most diverse and adaptable groups of animals: there are far more species of birds than of mammals, and they occupy a broad range of habitats. Birds and mammals split from a common ancestor over 300 million years ago. Yet certain bird species can perform complex mental tasks, including numerical problems, at levels similar to — and in some cases surpassing — primates, including great apes. Birds thus offer a privileged perspective on the cognitive functions underlying numerical abilities and their evolution. Moreover, birds provide excellent models for studying the ontogenetic development and neural mechanisms underlying numerical computations. In this Review, we provide a comprehensive picture of the contribution of avian studies to understanding numerical cognition, including behavioural laboratory studies, field studies and neurobiological investigations. We also critically examine the methodologies, interpretations and limitations of selected key studies. By synthesizing current knowledge and situating it within the broader field of cognitive research, we highlight the importance of a comparative perspective in understanding the role of evolutionary convergence in the emergence of cognitive functions.