Ecology and Conservation of Magellanic and Galápagos Penguins in a Changing World

Abstract

Climate change is rapidly altering the environment that wildlife experience, influencing their performance, ecological interactions, and population dynamics. Penguin species are threatened across the Southern Hemisphere and serve as indicators of environmental change and charismatic ambassadors for conservation. Focusing on two species of South American penguins, I leveraged field studies and remote sensing to test ecological hypotheses surrounding wildlife responses to global change as well as to ask applied questions with the aim of informing the management of threatened species. First, I examined the consequences of climate-driven delays in breeding in Magellanic penguins (Spheniscus magellanicus). Changes in phenology (i.e., the timing of important life events like growth, migration, and breeding) are widespread organismal responses to climate change that have been observed across taxa worldwide. Elucidating the impacts of these shifts is difficult yet essential for predicting how populations will be affected by global change. I explored the interaction between the timing of egg laying and subsequent breeding-season events like fledging at a large colony of Magellanic penguins at Punta Tombo, Argentina (Chapter 1). I found that differential shifts in events within the breeding season—hatching delayed while fledging dates did not—led to a shortened nestling period and reduced growth in chicks, with implications for their survival. Next, I tested for increasing temporal mismatch between penguin breeding and the window of optimal oceanographic conditions and resource availability (Chapter 2). I found evidence that Magellanic penguins cope with high environmental variability by matching long-term averages of resource phenology instead of tracking yearly conditions. As breeding delayed, however, fewer penguins bred at this optimal time. Together these chapters reveal the mechanisms by which climate-driven phenological shifts affect individuals and populations. The chapters highlight the importance of examining phenology across multiple annual-cycle events as well as considering how environmental variability and natural history together shape the outcomes of phenological shifts. My other dissertation chapters focused on the rare and endangered Galápagos penguin (Spheniscus mendiculus). These chapters aimed to reveal components of Galápagos penguin natural history, behavior, and demography that will aid in designing effective management strategies. First, I tested the accuracy of less invasive methods (i.e., measuring morphological features) for determining the sex of individual penguins (Chapter 3). Next, using this newly established method for sexing Galápagos penguins, I developed the first Bayesian, hierarchical mark-recapture model to estimate survival probabilities of male and female Galápagos penguins (Chapter 4). This analysis accounted for imperfect detection of individuals, tag loss, and transience, which can each result in biased survival estimates. I found low estimates of survival and detection for this species, highlighting the challenges of data collection and the need for cutting-edge quantitative tools to accurately estimate demographic rates and population trends for this rare and endangered seabird.