Evolutionary versatility of the avian neck

Bird necks display unparalleled levels of morphological diversity compared to other vertebrates, yet it is unclear what factors have structured this variation. Using three-dimensional geometric morphometrics and multivariate statistics, we show that the avian cervical column a hierarchical morpho-functional appendage, with varying magnitudes ecologically driven osteological variation at different scales organization. Contrary expectations given widely ecological functions in species, find regional modularity neck highly conserved, an overall structural blueprint significantly altered only by most mechanically demanding functions. Nevertheless, morphologies vertebrae within subregions more prominent signals adaptation pressures. We also both length allometry nature elongation birds are from vertebrates. In contrast mammals, isometrically head mass and, contrary previous work, achieved predominantly increasing vertebral lengths rather than counts. Birds therefore possess spine may be unique its versatility among extant one that, since origin flight, has adapted function as surrogate forelimb varied niches.