Since the 1970s, artificially stabilized hydrology, increased presence of Common Carp (Cyprinus carpio), and invasion by a highly competitive cattail hybrid (Typha x glauca) have changed the nesting ecology of Western Grebes at Delta Marsh, Manitoba. To evaluate the impact of stressors within Delta Marsh on Western Grebes, I repeated surveys originally conducted by Nuechterlein (1975) on the nesting ecology of Western Grebes at Delta Marsh, and compared 2009/2010 breeding success and nesting ecology data with 1973/1974 data. Reductions in breeding success during 2009 and 2010 were primarily due to increases in rates of nesting losses from wave action. Nests destroyed by spawning Common Carp, and depredations by River Otters (Lontra canadensis) further contributed to nesting losses. Reestablishing stands of emergent bulrush around nesting islands and reducing the abundance of carp within the marsh might help return Western Grebe breeding success to rates recorded in the 1970s

Since the 1970s, artificially stabilized hydrology, increased presence of Common Carp (Cyprinus carpio), and invasion by a highly competitive cattail hybrid (Typha x glauca) have changed the nesting ecology of Western Grebes at Delta Marsh, Manitoba. To evaluate the impact of stressors within Delta Marsh on Western Grebes, I repeated surveys originally conducted by Nuechterlein (1975) on the nesting ecology of Western Grebes at Delta Marsh, and compared 2009/2010 breeding success and nesting ecology data with 1973/1974 data. Reductions in breeding success during 2009 and 2010 were primarily due to increases in rates of nesting losses from wave action. Nests destroyed by spawning Common Carp, and depredations by River Otters (Lontra canadensis) further contributed to nesting losses. Reestablishing stands of emergent bulrush around nesting islands and reducing the abundance of carp within the marsh might help return Western Grebe breeding success to rates recorded in the 1970s

Thesis (M. Sc.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on July 8, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Ecology, Department of Biological Sciences, University of Alberta. Includes bibliographical references.

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The Western Grebe (Aechmophorus occidentalis, WEGR) is a Species of Special Concern in Alberta, declining in distribution and abundance. I evaluated how environmental variables including emergent vegetation, human developments, and prey availability affected WEGR persistence and abundance on 43 lakes in Alberta that historically supported WEGR. Persistence and abundance of WEGR were correlated, and both were positively associated with shoreline bulrush (Scirpus lacustris) and human development within a 500m buffer surrounding the lake, while inversely associated with surrounding forest. Bulrush provides important habitat for nesting, and WEGR are likely to occur on the same large fish-bearing lakes that humans prefer for recreation. However, this relationship with development puts grebes at risk for disturbance and habitat lossa primary threat to endangered birds. I recommend shoreline vegetation be protected for the success of breeding grebes, and human activity around colonies should be kept to a minimum to curb further WEGR decline. / Ecology

The breeding biology of western grebe was studied at Bear River Migratory Bird Refuge, Utah in 1973 and 1974. More than 300 nests were located and data gathered on nesting habitat and success. Western grebe at Bear River selected nest sites for nearness to open water of approximately 30 em in depth. At least one young was hatching in 21 percent of the nests. Avian predation and abandonment of nests following drops in water levels caused the greatest loss of nests. Chlorinated hydrocarbons monitored in western grebes showed DDE, DDD, PCB, 1260, and PCB 1254 levels in 24 breast muscle samples (wet weight) to average 12. 8, 0. 8, 3. 8, and 3. 5 ppm respectively. Contaminant concentration was found to be correlated to the condition of the bird as determined by visceral fat content. A significant (p<. 01) 2. 3 percent decline in western grebe eggshell thickness between preand post-DDT use periods was found. DDE was significantly (p<. 05) negatively correlated with eggshell thickness in western grebe. Contaminants were not linked to any reproductive failure in western grebe at Bear River MBR.