Allometry and integration do not strongly constrain beak shape evolution in large-billed (Corvus macrorhynchos ) and carrion crows (Corvus corone )

A recent geometric morphometric study on certain landbird lineages revealed that a major part of the variation in beak shape is accounted for by skull size and cranial shape. The study interpreted this result as evidence for the presence of strong evolutionary constraints that severely prevented beak shape from evolving substantially away from predictions of allometry and morphological integration. However, there is another overlooked but...