Fit for purpose? Analysis of the relationship between skull, beak shape and feeding ecology in Psittaciformes

Psittaciformes have a broad distribution across the southern hemisphere, and this wide ecological range is coupled with high levels of morphological diversity, particularly in the skull and beak structure, which has been previously linked to diet and body size. This paper studies how the beak and cranial shape vary in relation to predominant diet across a broad taxonomic range of parrots, using 2D geometric morphometric techniques and regression analyses. The data suggest that whilst there are some levels of significance between diet and beak shape, body mass was a much stronger co-variate. This indicated that skull morphology is more likely explained by parrot body mass and that whilst diet may partially explain beak shape in parrots when compared to other avian groups, it is not determining beak shape within the clade. Further study into other factors related to beak morphology, such as bite force, may prove key in explaining the evolutionary forces shaping the skull in parrots and other birds.