Abstract
Seabirds are vital links between marine and terrestrial ecosystems but are among the most threatened vertebrate taxa. Increasing our understanding of the habitat requirements, dispersal ability, and physiological constraints of seabirds is vital to informing conservation and management plans. Here, I explore the topics of foraging ecology, population structure, and diving physiology in a suite of seabird species in New Zealand and South Florida. I begin by characterizing the isotopic niche of Fiordland Penguins/Tawaki (Eudyptes pachyrhynchus) across the species’ range during the breeding season. Both δ13C and δ15N values varied among colonies with a trending towards higher δ13C and δ15N values and wider isotopic niches during the chick guard period. Indicating a reliance on wide range of prey species to feed themselves and their growing chicks. In the pre- molt period which follows, Tawaki are remarkably similar isotopically to the breeding season. This suggests that coastal foraging on the return journey to the mainland is crucial for fueling the molt. Overall, Tawaki have not experienced significant changes in trophic position or foraging area over the last 150 years. Next, I assessed the population structure of Tawaki as well as Erect-crested Penguins (Eudyptes sclateri) and Eastern Rockhopper Penguins (Eudyptes filholi). Tawaki exhibited no population structure and high gene flow throughout their range. I found very high co-ancestry within the Eastern Rockhoppers, suggesting limited genetic diversity in their shrinking population. Erect-crested Penguins exhibited population structure between the Antipodes and Bounty Islands groups. Finally, I characterized the mechanisms of O2 storage and muscle metabolism in the Double-crested Cormorant (Nannopterum auritum) and the Anhinga (Anhinga anhinga) in South Florida. The Double-crested Cormorant has a more oxidative phenotype fueled by large muscle-O2 reserves, particularly in the gastrocnemius. The Anhinga has a unique phenotype that is less reliant on aerobic ATP generation and has a high glycolytic capacity.