Meeting Abstract
Piscivorous birds have a unique suite of adaptations to forage under the water. One method of fishing for aerial birds is the plunge dive, wherein birds dive from a height to overcome drag and bouyancy in the water. The kingfishers are a well-known clade that contains both terrestrially foraging and plunge-diving species, allowing us to test for morphological and performance differences between foraging guilds. Diving species have narrower bills in the dorso-ventral and sagittal plane and longer bills (size corrected data, n=71 species, p<0.001 for all), Although these differences are confounded by phylogeny (phylogenetically corrected ANOVA for dorso-ventral p=0.24 and length p=0.13), beak width in the sagittal plane remains statistically different (p<0.001). We examined the effects of beak morphology on plunge performance by simulating dives with physical 3D printed models of kingfisher beaks coupled with an accelerometer, and through computational fluid dynamics (CFD). From simulated dives of bill models, diving species have lower peak decelerations, and thus, enter the water more quickly, than terrestrial and mixed-foraging species (ANOVA p=0.002), and this result remains unaffected by phylogeny (phylogenetically corrected ANOVA p=0.04). Preliminary CFD analyses confirm these trends in three representative species, and indicate that the morphology of the angle between the beak and head is a key site for avoiding additional drag in aquatic species.
