Nest‐Site Selection, Success, and Response to Predators by Cinnamon Teal and Other Ground‐Nesting Ducks in the Wetlands of Great Salt Lake, Utah

The wetlands of Great Salt Lake once supported hundreds of thousands of nesting ducks each year. In recent years, the number of nesting ducks in the same area was a fraction of those historic numbers. While many species of ducks do not rely on these wetlands for primary nesting habitat, cinnamon teal (Spatula cyanoptera) do. Great Salt Lake and its associated wetlands are in the heart of the cinnamon teal breeding range, and once supported half of the continental population. These wetlands are unique from other wetlands where waterfowl nest because they are artificially created using dams to hold water in large ponds. The vegetation on the dams provides most of the upland nesting habitat in wet springs, as the impoundments fill with water. Nest predators, who depredate duck nests, easily search these narrow trips of vegetation along the sides and tops of the dam. To be successful at nesting, a duck can hide its nest from predators by selecting a nest site situated in tall and thick vegetation, concealing it from the view of avian predators flying overhead and mammalian predators viewing the nest from the side or at ground level. A duck can also select a nest site concealed from predators that use their sense of smell (olfaction) rather than sight to locate nests. Olfactory concealment comes in the form of vegetation with a rough surface that creates turbulence and breaks up the odor plumes emitted from a duck sitting on its nest making the odor plume difficult to find and follow. Predators find and destroy nests regardless of weather conditions throughout the spring and early summer. Most predator visits to nests occurred during the periods before and after the new moon, when little illumination from the moon is present. When a predator chases a hen off its nest, there is only a 21% chance the hen will return to the nest, a 90% chance that it will incubate the nest, and only a 5% chance that the nest will go on to successfully hatch an egg