Investigating the convergent evolution of nectar-feeding birds through the lens of biomechanics

Abstract

Nectar-feeding birds employ highly specialized mechanisms to collect minute liquid rewards hidden within floral structures. There are over 20 independent evolutionary origins of nectarivory amongst birds, but little is known about how most of these lineages ingest nectar. In this dissertation, I examine the feeding mechanics of two distantly related nectarivorous bird groups and investigate the effects of nectar concentration on energy intake rates. In Chapter 1, I review what is known about avian nectar-drinking mechanics and define the knowledge gaps that should be addressed to understand how the multitude of nectar-feeding birds are able to consume their liquid food. In Chapter 2, I investigate if convergent morphologies underlie convergent biomechanics of nectar-feeding in two distantly related bird clades: sunbirds (family Nectariniidae) and hummingbirds (family Trochilidae). In Chapter 3, I describe the drinking mechanics of a morphologically unique group of nectar-feeding birds, the hanging parrots (genus Loriculus), and compare them with the mechanics of birds with more “typical nectarivore” feeding apparatus morphologies. In Chapter 4, I use the liquid-ingestion mechanics that I described for sunbirds to predict the nectar consumption rate and energy intake rate of multiple species feeding from a range of nectar concentrations. Using biomechanics to examine the variety of nectar-feeding mechanisms in birds unveils unique biological solutions to complex physical challenges. In turn, these mechanisms can be used to predict and test how different nectar-feeding birds interact with the variety of plant species they encounter in nature and what environmental factors shape their ecological interactions and evolutionary trajectories.