Date of Completion

8-15-2014

Embargo Period

8-7-2016

Keywords

Feeding Mechanisms | Fluid Dynamics | Hummingbird Foraging

Major Advisor

Margaret A. Rubega

Associate Advisor

Robert K. Colwell

Associate Advisor

Kurt Schwenk

Associate Advisor

Tai-Hsi Fan

Associate Advisor

Carl D. Schlichting

Field of Study

Ecology and Evolutionary Biology

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

My research aims to answer the questions: How do hummingbirds feed? And, how do the mechanics of feeding define the limits and adaptive values of feeding behaviors? I meticulously study every step of nectar capture and ingestion. My dissertation chapters are organized following a morpho-functional and feeding sequence approach: 1) Feeding Apparatus Morphology; with emphasis on the understudied morphology of the tongue grooves and bill tongue coupling. 2) Tongue Tip Dynamics; how hummingbird tongues entrap nectar. 3) Tongue Grooves Functioning: how the tongue acts as an elastic micropump while collecting nectar. 4) Bill Tip Mechanics; internal bill structures that aid in offloading nectar from the tongue. 5) Intraoral Transport: how the nectar flows inside the bill to the throat where it can finally be swallowed.

My results demonstrate that capillarity equations are unsuitable to calculate energy intake rate, which is the building unit of foraging theories; therefore a development of a new theoretical framework to study hummingbird energetics and foraging ecology is needed. I describe previously unknown methods of tongue-based nectar collection, report undocumented tongue and bill structures, and offer the first test of intraoral transport hypotheses.

I followed the scientific method cycle of deduction and induction. To understand the determinants of hummingbird feeding mechanics in an ecological context, I tested biophysical model predictions using data from wild birds.

Elucidating the drinking mechanism of hummingbirds will facilitate downstream calculations of the rates at which birds can obtain nectar along several environmental axes (e.g. altitudinal and latitudinal ranges, migrations, corolla morphology, etc.). This will in turn inform how and where the limits of nectar uptake have shaped the distribution, ecology and evolution of hummingbirds.

With their enchanting appeal and unique physical capabilities, hummingbirds captivate people of all ages. As such, they serve as ambassadors to the natural world, fostering public appreciation for scientific and conservation efforts aimed at preserving these fascinating birds, and the biodiversity upon which they depend.

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