From Extirpation to Extinction: Holocene Range Collapse of the Great Auk (Pinguinus Impennis)

Seabirds are the most threatened group of living birds, with a legacy of pronounced avian extinctions on islands and coastlines extending through the Holocene and historical periods. One such loss was the Great Auk (Alcidae: Pinguinus impennis), a large (~5 kg) flightless seabird found across the North Atlantic. While much research has been conducted on the species across its eastern range, virtually nothing is known about its western range. Great Auk populations were overexploited earliest in Europe during the Upper Pleistocene, leaving Iceland as the seemingly 'last' refuge for a colony with a final capture in 1844. In this research, we apply a conservation paleobiology lens to reconstruct the spatiotemporal dynamics of range collapse precipitating its extinction on both coasts, with a focus on investigating whether the Gulf of Maine may have been a last stronghold for the species. Great Auks are known to have occurred in Maine based on archaeological records and historical sightings. We comprehensively surveyed the literature to compile a dataset of 142 associated (134) and direct (8) radiocarbon dates for the Great Auk across its entire range, categorized by quality using a standardized ranking scheme. As the last appearance is likely not the last true individual, we applied a Gaussian-resampled, inverse-weighted McInerny (GRIWM) model to estimate extinction dates for different regions of its range. We repeated this process for sighting dates, compiling 92 unique Great Auk sightings that we ran in the Solow and Beet model. We compared extinction timing results between these two data types, and applied paleobiological techniques, including standard morphological metrics, to untangle the ecological dynamics of extinction. We found that there is greater uncertainty for the extinction timing of the North-West Atlantic Great Auk population, and there are not enough recent direct radiocarbon dates to assess when the Great Auk went extinct in that part of its range, including Maine. We also confirmed that Maine Great Auks are not morphologically distinct from other populations, aligning with existing studies. Furthermore, we conducted population viability analyses and discovered that low harvest rates (<1%) guaranteed extinction within 350 years. This thesis provides novel information on the Maine population, and contextualizes the Great Auk's extinction within a larger range collapse across the Atlantic. Studying the process of range collapse for an extinct Holocene species can recontextualize trends for extant species in Maine, such as the Atlantic puffin (Fratercula arctica).