Winter Ecology of Waterfowl on the Great Salt Lake, Utah.

摘要

My research provided new information regarding the ecology of waterfowl using the Great Salt Lake (GSL) during winter (November-April). Aerial survey results from winters 2004-05 and 2005-06 suggest ducks rely on hypersaline areas of GSL to a greater extent when availability of freshwater habitats is reduced. Total duck use in winter was 33% lower in 2004-05 compared to 2005-06 because of reduced freshwater habitat availability and lower GSL surface elevations resulting from persistent drought conditions. In winter 2004-05, 35% of total duck use occurred in hypersaline strata of GSL compared to only 15% in 2005-06. Occurrence of ice in freshwater and brackish strata was also associated with greater use of hypersaline strata. Common goldeneye, northern shoveler, and green-winged teal comprised ≥62% of mid-winter duck abundance and ≥94% of hypersaline use by ducks. On average, 68% of common goldeneye diet consisted of brine fly larvae. Brine shrimp cysts comprised 52% of northern shoveler diet and 80% of green-winged teal diet during winter. Thus, these species use halophile invertebrates to meet energetic and nutritional needs during winter at GSL. Lipid reserves of common goldeneye were 17% lower in winter 2004-05 when aquatic habitats were reduced and indices of brine fly larvae in GSL were lower. Mean lipid reserves declined 34% during winter consistent with an endogenous pattern of lipid loss common to wintering waterfowl. Female goldeneye also exhibited a declining trend in lipids as freezing conditions persisted whereas males generally maintained greater lipid reserves at lowest observed temperatures. Regional and local environmental conditions at GSL including Ephydridae productivity, freshwater habitat availability, and effective temperature likely play a more prominent role in lipid reserve dynamics for goldeneye than energetic costs of osmoregulatory adjustments. Wintering ducks using the GSL apparently accumulated high amounts of mercury (Hg) and selenium (Se) during winter. More than 30% of common goldeneye liver samples contained potentially harmful levels of Hg and Se. All northern shoveler liver samples contained elevated Hg concentrations and most (79%) displayed elevated Se concentrations. Further research is needed to evaluate the effect of these elements and their dynamics on GSL waterbirds.