S9-2.1 Jan. 6 Feeding mechanisms in birds RUBEGA, M.A.; University of Connecticut email@example.com
The most striking feature of avian feeding is the enormous degree of diversity, and the relative speed with which it evolved. The rapid evolution of the Neornithes, and the resultant (and persistant) difficulty of resolving the phylogenetic relationships among the extant clades of birds makes resolving evolutionary patterns of diversification in avian feeding mechanisms similarly difficult, but a few major themes emerge. Although tooth loss or reduction is widespread in vertebrates, birds are one of only two vertebrate lineages (turtles are the other) to exhibit total tooth loss; no extant species of bird possesses teeth. In both cases (birds and turtles) tooth loss is coupled with the covering of the jaws with a keratinaceous beak. However, birds differ in exhibiting dramatic diversification in the form of the jaws and beak, which is in turn associated with diversification in prey, the medium in which prey are taken, and the mechanics of prey capture. This diversification in birds may be attributable to the coupling of flight with the acquisition of a toothless beak. Convergence on similar morphology when similar prey are taken appears widespread (e.g., insectivory appears to have evolved repeatedly, accompanied by similar approaches to capture and similar jaw shapes), yet divergent morphological and mechanical solutions to the same problem are also common (e.g., piscivores differ substantially in mechanisms of prey capture and morphology). Compared to most other major vertebrate groups, there are still some very significant gaps in our understanding of the mechanics of feeding. For instance, direct observations of the use of the tongue during feeding by birds are limited to a very few species. Our understanding of the evolution of feeding morphology and mechanisms in birds would be greatly improved by resolution of the higher-level phylogenetic relationships among modern birds and more phylogenetically-directed sampling of study taxa.