Date of Award:
Master of Science (MS)
Michael R. Conover
Frank P. Howe
Karin M. Kettenring
Eared Grebes (Podiceps nigricollis) are migratory birds that build their nests over water and in large groups called colonies. Their typical breeding range is in central southern Canada and northern United States; however, a previously uncertain number of Eared Grebes (grebes) also nest around the Great Salt Lake (GSL), Utah, at the southern edge of their breeding range. Little is known about the habitat requirements for grebe nesting colonies at such low latitudes and if they are different from colonies found elsewhere. My objectives for this research were to determine the status of the grebe nesting population as well as their habitat characteristics along the GSL in freshwater wetlands. I found over 4,280 grebe nests distributed among 35 colonies. Grebes built nests by mounding submerged aquatic vegetation (SAV) beginning the first week of June. The results from my habitat study show that grebes prefer to nest in areas with an average water depth of 48 cm, high invertebrate density, and abundant areas of floating SAV. Water depth and vegetation type at colony sites as well as timing of nesting and average number of eggs per nest of GSL colonies differed from colonies located at more northern latitudes. The differences in nesting could be attributed to the need to wait for SAV to grow and form mats on the water’s surface, or a need to wait for their food source to reach harvestable size.
After grebes leave their nesting grounds, they stop at the GSL where they prepare for their final migration southward by consuming their fill of brine shrimp (Artemia franciscana). Brine shrimp are tiny invertebrates that are well-adapted to salty environments; they produce hard-walled eggs called cysts which are of great economic value and are commercially harvested from the GSL. I compared cyst viability, which is the percentage of cysts in a condition conducive to hatching, for cysts that had passed through the digestive tract of grebes and cysts samples obtained from the GSL. Only 30% of the cysts that had passed through grebes were viable, whereas 63% of cysts from the GSL were viable.
Delahoussaye, Leah M., "Eared Grebe Nesting Ecology and Chronology Along the Great Salt Lake, Utah" (2019). All Graduate Theses and Dissertations. 7524.
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