The reproductive success of the hooded merganser (Lophodytes cucullatus) at Mosquito Creek Wildlife Management Area /

Abstract

The goal of this study was to examine factors that influence the reproductive success of hooded mergansers, Lophodytes cucullatus, nesting at Mosquito Creek Wildlife Management Area (MCWMA). I examined nesting activities of the hooded merganser at MCWMA from March through July 1998. I collected at least two unincubated hooded merganser eggs from active nests to determine eggshell thickness and organochlorine (OCs) concentrations. My data were compared with an intensive study of nest boxes at MCWMA in 1994 and 1995 and with previous studies and historical collections ofeggshells. The mean eggshell thickness ofhooded merganser eggs was 0.605±0.004 mm, 9% thicker than a previous study done in 1981. Based on eggshell thickness, it appears that OCs are not a concern. However, results of this study indicate a population of nesting hens that appear to be stressed by high nest density. An increase in nest box use from 21% (1994-1995) to 33% (1998) was inversely correlated with a decrease in nesting success from 80% (1994-1995) to 69% (1998). In addition, a significant decrease in hatching success was noted from 90% (1994-1995) to 79% (1998) (p<0.05) while intraspecific nest parasitism increased from 13% (1994-1995) to 75% (1998). In conclusion, it appears that reproduction in this population ofhooded mergansers is being influenced by nest box management, which promotes high density nesting, high levels of parasitism and nest abandonment, and not by external factors, such as environmental contaminants.