Doctor of Philosophy
MacDougall-Shackleton, Elizabeth A.
MacDougall-Shackleton, Scott, A.
Seasonal migration exposes animals to a variety of habitats and parasites, and if infected migratory birds migrate successfully there is great potential for birds to transport infectious diseases long distances. Our current understanding of whether birds contribute to the spread of disease relies upon observational field studies that are limited in their ability to discern cause from effect. Using captive and field-based experiments for my doctoral research, I answered three research questions: (1) are nocturnal migratory restlessness (Zugunruhe) and body condition affected by mounting an acute phase immune response during migration; (2) what are the impacts of parasitic infection on Zugunruhe and body condition compared to those of upregulating immunity, and (3) are the observed consequences of successful parasite infection in captive conditions also realized in nature? Contrary to expectations, song sparrows (Melospiza melodia) and white-throated sparrows (Zonotrichia albicollis) challenged with lipopolysaccharide (LPS) and/or keyhole limpet hemocyanin (KLH) in captivity during autumn migration exhibited increases in body condition and did not reduce Zugunruhe. Finding no negative impacts of short-term immune challenges on migratory traits suggests that short-term activation of the acute immune response does not constrain migratory activity or preparation in these songbirds. Successful Plasmodium infection in captive white-throated sparrows did not reduce body condition but did reduce Zugunruhe once peak parasite loads were reached, two weeks after inoculation. In contrast, birds exposed to Plasmodium that did not become infected (resistant) exhibited reduced Zugunruhe immediately after exposure but did not differ from controls (not exposed) two-week after inoculation. Resistant song sparrows exposed to Plasmodium had reduced lean mass 12 days post-exposure in captivity. Once released, radio-telemetry tracking indicated no significant difference in the departure date between controls, infected, and resistant song sparrows. These results are the first to demonstrate that exposure to malaria can impact migratory traits, independent of infection. Contrasting captive and field-based results highlight the importance of using similar methodological timelines, hosts, and pathogens to draw concrete conclusions regarding the impact of disease on migration. These studies are the first to explore the impacts of upregulating immunity and parasitic infection in controlled captive conditions. In combination, these findings indicate that models predicting disease spread should consider resistant-induced effects on body condition and migration alongside infection-induced effects.
Kelly, Tosha R., "Hitchhiker's guide to migration: effects of experimental parasitic infection and other immune challenges on migratory traits of sparrows" (2018). Electronic Thesis and Dissertation Repository. 5816.