It is common knowledge that birds, while having excellent sight and hearing, lack in the scent department. Interestingly enough, a few thousand years ago it was their sense of smell which was so heightened.
During the evolution from dinosaurs to birds, a keen sense of vision, hearing and balance developed. It was previously thought that smell was of lesser importance to birds while developing much needed senses of balance and vision for flight.
However, the latest research shows that the sense of smell actually improved during this stage.
Scientists compared the olfactory bulbs (part of the brain involved with smell) of ancient dinosaurs to the birds of today. They found that the sense of smell increased in the early stages of bird development as they were competing with dinosaurs at this time.
The detailed research which was carried out involved using CT scans to reconstruct models of dinosaur and extinct bird skulls. Although the brain tissue of these creatures is long gone, scans made it possible to visualise and generate 3D computer representations of the brain parts. It was then possible to determine the size of olfactory bulbs within the different brains.
Through this research, details of how birds inherited their sense of smell were discovered. The oldest known bird inherited its sense of smell from a carnivorous dinosaur. This all happened around 150 million years ago. Later, about 95 million years ago, the ancestor of all birds today evolved an even better sense of smell.
Direct comparisons between ancient and modern-day birds have also been highlighted. One such ancient bird, Archaeopteryx, had a sense of smell similar to that of pigeons and relied on smells for numerous behaviours. Others need smell for navigation. Then there are the many birds which rely on smell to search for food, much like dinosaurs when they hunted for grub.
The most common birds that humans encounter today have small olfactory bulbs and weaker smell ability. So why do modern-day birds have a reputation for a poor smell of smell, contradicting that of their ancestors? The reason is simple … modern-day birds are cleverer. They therefore do not have to rely on smell as much for survival.
Makes you think twice about using the saying “bird brain” again!
Source: Journal Reference: D. K. Zelenitsky, F. Therrien, R. C. Ridgely, A. R. McGee, L. M. Witmer. Evolution of olfaction in non-avian theropod dinosaurs and birds. Proceedings of the Royal Society B: Biological Sciences, 2011; DOI: 10.1098/rspb.2011.0238
Viewed online [http://www.sciencedaily.com/releases/2011/04/110412201724.htm]