Breeding Ecology of Harlequin Ducks, Alaska Department of Fish and Game, Eastern Prince William Sound, 1991-1993

Breeding habitat and productivity of harlequin ducks was studied in eastern
Prince William Sound (EPWS), Alaska, during 1991 - 1993. Harlequin ducks usually selected the largest anadromous salmon streams available for nesting. Volume discharge of breeding streams averaged 3.2 m3/s and was the strongest variable distinguishing between streams used and not used by breeding harlequins. Ten nests of harlequins were located on southwest-facing, steeply-sloped banks of first order tributaries near timberline elevations.
Nests were associated with woody debris and shrubs, in shallow depressions or cavities, and beneath the canopy of old growth forest. Productivity of harlequin ducks in EPWS was low relative to other breeding populations. Nest density for 7 streams was approximately 0.3 - 0.5 breeding females per km. Estimated breeding propensity of adult females was 86% in 1991 and 74% in 1992. Average clutch size for 8 nests was 6.1 eggs.
Duckling mortality was estimated at 59%, occurring mostly during 15 - 35 days of age.
Average brood size at fledging was 2.50 and recruitment was estimated at 0.6 - 1.1 per breeding female. Coastline densities of broods during 1991 - 1993, respectively, was 2.3, 0.9, and 1.8 per 100 km.

1991年至1993年间，研究团队在阿拉斯加东部威廉王子湾（Eastern Prince William Sound, EPWS）开展了丑鸭（Harlequin Duck）的繁殖栖息地与繁殖生产力相关研究。丑鸭通常会优先选择区域内规模最大的溯河洄游性鲑鱼溪流（anadromous salmon streams）作为筑巢位点。繁殖溪流的径流量均值为3.2 m³/s，该指标是区分繁殖丑鸭所利用与未利用溪流的最显著判别因子。
研究人员在林线（timberline）海拔附近的一级支流（first order tributaries）西南朝向的陡坡岸带，共发现10处丑鸭巢穴。巢穴多紧邻木质残体与灌丛，建于浅洼或树洞之中，且位于老龄林（old growth forest）的林冠下方。
阿拉斯加东部威廉王子湾的丑鸭繁殖生产力相较于其他繁殖种群偏低。7条监测溪流的巢穴密度约为0.3~0.5只繁殖雌性/千米。成年雌性丑鸭的繁殖倾向（breeding propensity）估算值在1991年为86%，1992年为74%。8处巢穴的平均窝卵数（clutch size）为6.1枚。
丑鸭雏鸭死亡率约为59%，死亡主要集中在孵化后15至35日龄阶段。雏鸟出飞（fledging）时的平均窝雏数为2.50只，每只繁殖雌性对应的种群补充（recruitment）个体数估算值为0.6~1.1只。
1991年、1992年、1993年的海岸带育幼群密度分别为每100千米2.3只、0.9只、1.8只。