HABITAT-RELATED VARIATION IN MOVEMENTS AND FLEDGING SUCCESS OF AMERICAN BLACK DUCK BROODS IN NORTHEASTERN NOVA-SCOTIA

Female American black ducks (Anas rubripes) are known to move their br oods from low- to high-nutrient rearing sites. We studied the extent o f brood movement and fledging success in a northeastern Nova Scotia wa tershed. Annually, about half the broods moved either overland or alon g three rivers from small, widely dispersed oligotrophic - mesotrophic wetlands to a large hypertrophic tidal marsh. Mean brood size at fled ging was 3.50 in the tidal marsh but 7.05 at the dispersed freshwater wetlands. Females that remained at dispersed sites fledged more duckli ngs than females that moved to the marsh. Attrition occurred predomina ntly in the marsh or in transit. Females fledged fewer young when they raised broods at the marsh than when the same females raised broods a t inland sites. Females were as successful at nutrient-poor sites as a t nutrient-rich sites. The study suggests that concentrating birds in nutrient-rich sites may be counter productive in terms of female repro ductive fitness and population recruitment.