Oxidative State of Songbirds During Migration and Best Practices to Communicate the Science

Abstract

Managing oxidative stress is an important physiological function for all aerobic organisms, particularly during periods of prolonged high metabolic activity, such as long-distance migration. However, no previous study has investigated the oxidative status of songbirds at different stages of migration, whether that oxidative status depends on the condition of the birds, how birds use their condition in concert with access to free water to make stopover decisions, or the effects of oxidative challenges like flight on subsequent reproduction. Additionally, scientists undertaking such research are commonly expected to disseminate their results as a Broader Impact of their studies - typically to secure research funding - and often struggle to do so, given that they are not usually trained in non-technical communication or public engagement. In this dissertation, I introduce the fundamentals of oxidative balance in flying songbirds (Chapter 1), discuss physiological factors affecting the condition and behavior of migratory songbirds on stopover (Chapters 2 and 3), describe the impact of dietary antioxidants and flight exercise on songbird reproduction (Chapter 4), and present a framework of guiding principles to help researchers communicate their science (Chapter 5). Development of this framework influenced the style and approach of the dissertation as a whole, with each chapter’s organization and figure design benefiting from lessons transferrable from communication with non-scientist audiences to communication with professional peers. To investigate the relationship between energy stores and oxidative status of long-distance migratory birds on stopover, I drew blood samples from two species of Neotropical migrant (Blackpoll Warbler, Setophaga striata, and Red-eyed Vireo, Vireo olivaceus) with differing migration strategies during autumn migration on Block Island, USA, and a species of trans-Saharan migrant (Garden Warbler, Sylvia borin) during spring migration on the island of Ponza, Italy; I found fat stores to be positively correlated with circulating antioxidant capacity in Blackpoll Warblers and Red-eyed Vireos and positively correlated with circulating lipid oxidation levels in all three species. Among Garden Warblers, oxidative damage levels decreased with time on stopover (up to 8 nights). Thus, the physiological strategy of migrating songbirds appears to be to (1) build prophylactic antioxidant capacity in concert with fuel stores at stopover sites before a long-distance flight, and (2) repair oxidative damage while refueling at stopover sites after long-distance flight. To assess the contribution of free water to migratory birds’ stopover decisions, I captured 61 free-living Garden Warblers in spring at a frequently used stopover site in the Mediterranean