<p>Studies of biomechanical adaptations in birds have often relied on the analysis of isolated bone sections, limiting our understanding of spatial patterns across the entire diaphysis. This study examines the hypothesis that vascular canal organization in the humerus of mallards (Anas platyrhynchos) is biomechanically optimized and has remained stable since the Late Pleistocene. We analyzed the spatial distribution of four vascular types—laminar, reticular, radial, and longitudinal—across 24 levels of the humeral diaphysis in 11 fossil specimens from the Binagadi asphalt deposits (Azerbaijan) and 4 recent specimens, using histological sections and repeated-measures ANOVA. Results revealed no significant difference in the mean proportion of any vascular type between groups, demonstrating remarkable stasis over millennia. However, a significant Level × Group interaction for laminar vascularization (<i>p</i> = 0.005) revealed a spatial reorganization, with recent specimens exhibiting a more pronounced concentration in torsion-resistant medial regions (up to 68.56%). This suggests conserved biomechanical function alongside a potential fine-tuning of the structural response to flight loads. The predominance of specific vascular types near muscle entheses (e.g., reticular/radial near the m. deltoideus major enthesis) underscores the role of localized mechanical stress in shaping bone microstructure. This study provides a novel diaphyseal-level framework for interpreting bone functional adaptation, offering insights into long-term biomechanical stability in birds and a valuable tool for the paleontological identification of fossil fragments.</p>