TRACKING AVIAN ABUNDANCE THROUGH THE MEDIEVAL WARM PERIOD AND LITTLE ICE AGE

Recent excavation work in a late-Holocene paleontological site (Lamar Cave) located in Yellowstone National Park (Wyoming, USA) has revealed a remarkably rich faunal assemblage that includes thousands of vertebrate remains from mammals, birds, amphibians and fish. In this site, mammals are the most abundant and studies of several small mammals have already documented changes in abundance, morphology and genetic structure that appear to be correlated with Late Holocene climate changes (3,000 ya-present). Here, we reinvestigate the influence of climate change on the local fauna in Lamar Valley by focusing on the bird remains of Lamar Cave, which constitute about 1,000 bones. Although birds are well-studied behaviorally and occupy a wide range of niches, avian paleoecological studies of the Holocene are rare. This millennial timescale provides a critical test of avian biotic response to predictions made by global change scenarios. Comparison of patterns in abundance shifts in mammal versus bird species through the last 3,000 years accentuates that population sizes change most rapidly during the Medieval Warm Period and Little Ice Age. For birds, this conclusion is based on data from the two most abundant bird lineages, grebes (Podiceps nigricollis) and passerines (Passeriformes). Analysis is ongoing on other common and ecologically diverse groups, including grouse (Dendragapus obscurus and Bonasa umbellus), coots (Fulica americana), shorebirds (Charadriiformes), and ducks (Anas sp. and Mergus sp.).