Revisiting the nesting ecology of the western grebe after 40 years of changes at Delta Marsh, Manitoba

Abstract

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