Winter waterbird ecology on the Great Salt Lake, Utah, and interactions with commercial harvest of brine shrimp cysts.

摘要

My research examined wintering ecology of waterbirds on the Great Salt Lake (GSL), Utah, with special reference to interactions with the harvest of brine shrimp (Artemia franciscana) eggs (i.e. cysts). The GSL is an important body of water for many avian species due to its location in the arid Great Basin of the western U.S. In chapters 2 and 4, I examine variables that influence waterfowl and eared grebe (Podiceps nigricollis) populations, respectively. Northern shoveler (Anas clypeata) abundance was correlated with temperature while common goldeneye (Bucephala clangula) abundance was correlated with food availability. The presence of commercial harvest boats was not a factor in avian abundance or distribution. In chapters 3 and 5, I examine diet of waterfowl and eared grebes, respectively, and calculate the removal of brine shrimp cysts by birds. Northern shovelers and green-winged teal (Anas crecca) varied their diet based on the time of year. Both consumed wetland plant seeds in fall and spring, and salt-tolerant invertebrates throughout winter. Eared grebes consumed brine shrimp until December, when they increased consumption of cysts. Measurements of bird consumption rates indicated avian species removed less than 15% of the annual cysts removed by birds and the commercial harvest industry combined. In Chapter 6, I examined downed eared grebes and those that still occupied the GSL. Eared grebes collected pre-downing were heavier (523 g) than deceased birds (433 g). Mercury (4.4-25.8 ppm) and selenium (1.8-7.2 ppm) concentrations in both downed birds and those collected at the GSL were above levels observed to impact bird species. Though heavy metal concentrations may have impacted survival of downed birds, bad weather likely caused the mass downing. In Chapter 7 I used 2 data sources to describe the migratory connectivity of northern shovelers wintering on the GSL. Shovelers recovered at the GSL (n = 22) had been banded during the summer in southern Canada and northern Montana. Stable-isotope data placed the largest number of shovelers collected on the GSL as breeding in the western U.S. and southern Canada. Northern shovelers wintering on the GSL had shorter migration distances than conspecifics wintering elsewhere.