A comparative study of the functional morphology and ecology of insectivory in hummingbirds

Feeding is an aspect of animal performance that has clear consequences for individual fitness and morphological evolution. Hummingbirds (Family Trochilidae) are an excellent group for the study of feeding performance because they are a speciose family of small, hovering, nectar specialists evolved from insectivorous ancestors. My dissertation research explored the role of insectivory in the evolution and ecology of hummingbirds. Here I begin with a review of the interaction of diet, morphology, physiology, and ecology to illustrate the importance of insectivory to all aspects of hummingbird biology. ^ In the second chapter, I characterize variation in hummingbird beak morphology based on museum specimens and examine this variation with respect to diet and ecology in a phylogenetic context. I find that hummingbird beak length is variable but that the distal dimensions of hummingbird beaks do not vary with respect to beak width and depth. This narrowness in beak dimension is presumably driven by the physical demands of nectar transport, but may hinder effective arthropod capture and transport, representing a potential tradeoff in beak function. ^ In chapters three and four, I investigate how hummingbirds catch and consume arthropod prey. I use high speed videography to document the feeding behaviors, performance, and kinematics of six hummingbird species. I discover that hummingbirds use a novel form of dorsoventral mandibular flexion during aerial arthropod capture. I examine the mechanics of dorsoventral mandibular flexion and discuss the consequences of kinesis for arthropod capture and transport. This study of feeding mechanics and kinematics looks at variation in feeding performance at the individual and species level in a group of birds with two distinct modes of feeding to provide insight into how morphology, behavior, and phylogeny contribute to the evolution of specialization in diet and trophic structures.