Nest Site Selection by Eared Grebes in Minnesota

Abstract

This study examined nest site selection within Eared Grebe (Podiceps nigricollis) colonies in terms of nesting synchrony, nearest-neighbor distances, vegetation, exposure, and nest success. Nests in 11 Eared Grebe colonies in Minnesota were initiated over a span of 11-45 days, with most nests in each colony initiated in < 11 days. In each of six colonies studied, mean nearest-neighbor distance of the earliest nests was greater than that of the complete colony. Nearest-neighbor distance tended to decrease with an increase in emergent vegetation density. Early nests seemed to form the skeleton of a neighborhood, with later nests filling in or establishing other neighborhoods. In five of six colonies, clutch sizes were larger in earlier nests. No significant difference in egg volume between early and late nests was apparent in the two colonies studied. Early nests were more successful than were late nests in two of four colonies; center nests were more successful than were edge nests at only one of four colonies. Most nest destruction in this study was caused by waves generated by high winds; < 2% of nests showed evidence of predation.