Empty headed? Largest study of its kind proves bird brain is a misnomer

Empty headed? Largest study of its kind proves bird brain is a misnomer
by Simon Mansfield
Sydney, Australia (SPX) Jan 22, 2025

Understanding what birds think while in flight may seem impossible, but researchers in Australia and Canada have unveiled groundbreaking insights by studying the internal structure of birds' skulls. Scientists from Flinders University in South Australia and the University of Lethbridge in Canada have combined their expertise to digitally reconstruct the brain structures of living and extinct birds using innovative techniques.

The study, published in Biology Letters and conducted by the Bones and Diversity Lab at Flinders University alongside the Iwaniuk Lab at the University of Lethbridge, has revealed that even the skulls of long-deceased birds hold critical information about their brain structure. By using digital "endocasts" to recreate the space inside the cranial cavities of bird skeletons, the researchers gained detailed insights into the size and shape of key brain regions.

Lead author and Flinders University PhD student Aubrey Keirnan explained, "This showed that the two correspond so closely that there is no need for the actual brain to estimate a bird's brain proportions. While 'bird brain' is often used as an insult, the brains of birds are so large that they are practically a braincase with a beak. We decided to test if this also means that the brain's imprint on the skull reflects the proportions of two crucial parts of the actual brain."

The research team analyzed the skulls of 136 bird species, comparing the microscopic sections of the brains with their digital endocasts. This large-scale study found a nearly one-to-one correlation between the size of two key brain regions, the forebrain and cerebellum, and the surface areas of the digital endocasts.

Senior co-author Associate Professor Vera Weisbecker from Flinders University's College of Science and Engineering highlighted the technological advancements that made this research possible. "We used computed microtomography to scan the bird skulls. This allows us to digitally fill the brain cavity to get the brain's imprint, also called an 'endocast.' The correlations are nearly 1:1, which we did not expect. But this is excellent news because it allows us to gather insight into the neuroanatomy of elusive, rare and even extinct species without ever even seeing their brains."

She further emphasized the benefits of non-destructive scanning techniques. "In the old days, people needed to pour liquid latex into a brain case, wait for it to set, and then break the skull to get the endocast. Using non-destructive scanning not only allows us to create endocasts from the rarest of birds, it also produces digital files of the skulls and endocasts that can be shared with scientists and the public."

Professor Andrew Iwaniuk from the University of Lethbridge, a co-leader of the study, admitted he was surprised by the precision of the results. "While most of the telencephalon (outer part of the forebrain) is visible from the outer surface, a substantial portion of the cerebellum is obscured by this region. Additionally, the avian cerebellum has 'folds' which are often obstructed by a large blood vessel called the occipital sinus. Given that the degree of obscurity can vary between species, I did not expect a strong correlation between endocast surface area and brain volume across all species."

This research not only supports existing findings on the brains of critically endangered and extinct bird species but also raises questions about its application to dinosaurs, which are birds' closest extinct relatives.

"For example, crocodiles are the closest living relatives of birds, but their brains look nothing like that of a bird - and their brains do not fill the braincase enough to be as informative," said Ms. Keirnan.

Research Report:Avian telencephalon and cerebellum volumes can be accurately estimated from digital brain endocasts (2025)