Differential Vulnerability Patterns among Three Species of Sea Ducks

Abstract

During the 1969 and 1970 hunting seasons, 1,530 white-winged scoters (MeZanitta deglandi), surf scoters (M. perspicilla;ta), and common scoters (Oidemia ntgra) were observed responding to decoys in typical scoter hunting situations on the New Hampshire coastline. Results indicated that the common scoter was extremely vulnerable to actual hunting, the surf scoter was intermediate, and the white-winged scoter was the least vulnerable. These differences in vulnerability patterns influenced the composition of the scoter harvest as compared with the relative abundance of the three species on the study area. The literature indicates that changes in population levels and winter distribution of scoters have occurred. The described differences in vulnerability, coupled with past hunting pressure, provide a mechanism by which these changes could have happened. To more fully understand the future dynamics of scoter populations in relation to harvest, more accurate population measurements are needed. The sport of sea duck hunting is old and well established, especially along the New England coast, and many hunters enjoy the challenge of ocean shooting with the long seasons and liberal bag limits. Despite this long history of sport hunting, there is little available information concerning the effect of hunting on sea duck populations because of the presently inadequate sampling of the harvest by such surveys as wing collections, hunter mail questionnaires, and band recovery data. Differences in vulnerability of waterfowl, based on observations in hunting situations, were first described in 1965 (Olson 1965). From this work, Olson concluded that disproportionate sex ratios in canvasbacks ( Aythya valisiner?a ) were the result of differences in vulneralbility between sexand age-groups. He further suggested that differences in vulnerability probably affected the population structure of other waterfowl such as lesser scaup ( Aythya