Aging is associated with larger brain mass and volume in homing pigeons (Columba livia)

In mammals, the brain decreases in mass and volume as a function of age. The current study is, to the best of our knowledge, the first to investigate age-related changes in brain mass and volume in birds. Following perfusion, brains from young and old homing pigeons were weighed on a balance and orthogonal measurements of the telencephalon, cerebellum, and tecta were obtained with a digital caliper. It was found that older pigeons had heavier brains than younger pigeons, a difference that remained after controlling for body mass. Additionally, older pigeons had on average greater estimated telencephalon volumes than younger pigeons, again also after controlling for body mass. Cerebellum and right tectum volumes also differed between age groups after controlling for body mass, with older pigeons having a larger cerebellum and right tectum than younger pigeons. In sum, brains are on average heavier and larger in old pigeons, which display age-related cognitive decline, compared to young adult pigeons. The larger brain in older homing pigeons also lies in stark contrast with aging of the mammalian brain.