Spatial brain structures are selectively preserved during aging in homing pigeons (Columba livia), an avian spatial specialist.

Pigeons (Columba livia) rely heavily on spatial cognition for navigation. As such, this species is commonly used to investigate the neural correlates of spatial behaviours in birds, particularly the hippocampus and septum. As this species can live for decades when housed in the laboratory, several studies have recently used pigeons to examine long-term effects of aging on the brain, a concept that is less well-understood in birds compared to mammals. Studies assessing age-related structural plasticity in the pigeon brain have yielded mixed findings, possibly due to methodological differences. Here, we used Nissl-stained brain sections collected from homing (racing) pigeons (N = 29) ranging in age from 2 to 22 years old (divided into "adult", "old", and "very old" groups), and a standard histological volume reconstruction method, to assess brain-wide age effects (volume of the overall telencephalon) as well as effects specifically on spatial (hippocampus, septum) and non-spatial (entopallium) structures. Overall, we found that telencephalon and entopallium volumes declined with age, whereas hippocampus and septum volumes remained stable across the lifespan. We also detected a modest positive correlation between age and hippocampus volume, suggesting hippocampus volume increases as pigeons age, although this finding should be interpreted cautiously. Overall, our results suggest that in pigeons, neural structures and circuits supporting spatial cognition appear to be selectively preserved relative to other brain regions during aging, and more broadly, that age-related structural changes in the avian brain are not shaped only by generalized senescence, but by functional and behavioural demands placed on specific structures and circuits across the lifespan.