Bonneville Basin Avifaunal Change at the Pleistocene/Holocene Transition: Evidence from Homestead Cave

Although recent research of the faunal and floral remains of the Bonneville basin has increased our knowledge of biotic change at the end of the final regression of Lake Bonneville, our knowledge of avifaunal change during this period remains poorly understood. This study focuses on the bird remains from the lower strata (especially Stratum I) of Homestead Cave, the only site in the Bonneville basin that provides a substantial, well-dated avifaunal record dating to the terminal Pleistocene and early Holocene. Analysis of the entire Stratum I avifauna produced a sample of 4613 identified specimens; the fauna is dominated by aquatic taxa including ducks, grebes, gulls, and shorebirds. Terrestrial taxa are also well represented, most notably by Greater Sage-Grouse (Centrocercus urophasianus). We examine change in the taxonomic composition of the Bonneville basin aquatic avifauna as anticipated from previous research and find significant declines from 13.1 to 9.5 cal ka BP in piscivorous or deep-water taxa, such as diving ducks and Aechmophorus grebes. Our analysis captures the transition from the freshwater conditions associated with the terminal regressive phase of Lake Bonneville to the warmer hypersaline context that has characterized Great Salt Lake for much of the Holocene. We also document a dramatic loss of Greater Sage-Grouse across this period. This ~ 4000-year record of avifaunal change may prove useful in modern conservation efforts, most notably for that of Greater Sage-Grouse, as xeric conditions are forecasted to increase in the future.