Date of Award:

5-2016

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Wildland Resources

Advisor/Chair:

Michael R. Conover

Abstract

Despite the hemispheric importance of Great Salt Lake (GSL) as a staging area for migratory birds, little is known about the resources that GSL provides to these birds, or how changes to the GSL ecosystem might impact the avian community. Three species of migratory waterbirds that stage at GSL are Wilson’s phalaropes (Phalaropus tricolor), red-necked phalaropes (Phalaropus lobatus), and eared grebes (Podiceps nigricollis). My objective for this research was to study the impacts of prey availability on the staging ecology of these species. In Chapter 2, I examined the use of GSL habitats by both species of phalaropes. In the high-salinity bays of GSL, phalaropes were most strongly associated with shallow water. In the low-salinity bay, there were no strong associations between phalarope presence and particular habitat characteristics. In Chapter 3, I analyzed the behaviors of phalaropes relative to prey densities. Phalaropes commonly foraged in Carrington Bay, which had the highest densities of brine fly (Ephydridae) adults, and in Farmington Bay, which had high densities of benthic macroinvertebrates. Foraging behavior differed between Wilson’s and red-necked phalaropes, with Wilson’s phalaropes spinning more often than red-necked phalaropes.

In Chapter 4, I examined interannual and nightly variations in eared grebe fall migration departures in relation to prey availability and environmental conditions. Eared grebes began migration relatively early when lake temperatures were relatively warm, densities of brine shrimp (Artemia franciscana) adults were high, and densities of brine shrimp cysts were low. The likelihood that eared grebes would depart on a given night was positively associated with the average barometric pressure 12 hours prior to sunset.

The resources provided by GSL support substantial proportions of the staging populations of phalaropes and eared grebes. Management efforts should seek to maintain the habitats and resources needed by phalaropes and eared grebes at GSL. Future large-scale diversions of freshwater may threaten GSL’s suitability as a staging area for these birds.

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