ABSTRACT

Eared Grebes (Podiceps nigricollis) are colonial-nesting waterbirds that use waterbodies along Great Salt Lake (GSL), Utah, during the breeding season. We examined the habitat characteristics of nesting colonies established by Eared Grebes, including water depth, invertebrate biomass density, vegetation species, vegetation cover, waterbody area, distance to shore, distance to nearest emergent vegetation, and distance to GSL. Samples and measurements were taken during the summer of 2018 from inside Eared Grebe nesting colonies, outside colonies but within the same waterbody, and unused waterbodies that did not contain colonies. We compared colonies sites to non-colonies sites that were within the same waterbody using logistic regression to build models and found no differences between them, suggesting that space for a colony is not lacking within a colony waterbody. Colony waterbodies differed from unused waterbodies (those not containing a colony) in having deeper water and higher percent cover of submerged aquatic vegetation. Results from Eared Grebe colonies around GSL were compared to colonies found in a literature review. Water depth in colonies around GSL were shallower than colonies located elsewhere. All of the colonies in this study were established on mats of submerged aquatic vegetation as opposed to colonies in other studies that were built on emergent vegetation. Wildlife biologists around GSL can manage for nesting Eared Grebes by maintaining a water depth (35–55 cm) that is conducive for submerged aquatic vegetation growth and high invertebrate densities. Climate change models predict that the American Southwest, which is already arid, will become drier in the future. When combined with increasing diversions of water for human uses, the waterbodies where Eared Grebes currently locate their colonies may become entirely dry or too shallow in the future to sustain them. Received 24 March 2020. Accepted 10 October 2020.

This content is only available as a PDF.
You do not currently have access to this content.